1 Chapter- 13: S & P-BLOCK ELEMENTS Elements of group I-A (Alkali Meta ls) and Group II-A constitute s-block. They hae their alence electrons in s- orbital. !-block has only metals ho "e er hy dr ogen and helium are e#ceptions$ these t"o are non-metals. Elements of group III-A$ I%-A$ %-A$ %I-A$ %II-A and %III-A constitute p-block. They hae their alence electrons in p- orbital. &-block consists of metals as "ell as non metals. 'p till no" more than elements are discoered so chemists felt to classify them into groups of similar properties. (i) *locks+ The elements are diided into four blocks. (a) Th e e lements haing t heir alence electrons in s-sub shell are called s-block elements. T"o ertical columns on e#treme left of periodic table i.e. Group-IA and Group-IIA constitute s- block. (b) Th e e lements haing t heir alence electrons in p-sub shell are called p-block elements. !i# ertical column on e#treme right of periodic table i.e. Group-IIIA$ I%A$ %A$ %IA$ %IIA and Group-%IIIA constitute p-block. (c) Th e elements haing t heir alence electrons in d-sub shell are called d-block elements. Ten ertical column s in bet"een s-block and p- block of periodic table i.e. Group-I* to %III* constitute d-block. (d) Th e e lements haing t heir alence electrons in f-sub shell are called f-block elements. T"o hori,ontal ro"s on the bottom of periodic table i.e. anthanides and Actinides series constitute f-block.
Elements of group I-A (Alkali Metals) and Group II-Aconstitute s-block. They hae their alence electrons in s-orbital. !-block has only metals ho"eer hydrogen andhelium are e#ceptions$ these t"o are non-metals.Elements of group III-A$ I%-A$ %-A$ %I-A$ %II-A and %III-Aconstitute p-block. They hae their alence electrons in p-
orbital. &-block consists of metals as "ell as non metals. 'ptill no" more than elements are discoered so chemistsfelt to classify them into groups of similar properties.
(i) *locks+
The elements are diided into four blocks.
(a) The elements haing their alence electrons ins-sub shell are called s-block elements. T"oertical columns on e#treme left of periodictable i.e. Group-IA and Group-IIA constitute s-block.
(b) The elements haing their alence electrons inp-sub shell are called p-block elements. !i#ertical column on e#treme right of periodic
table i.e. Group-IIIA$ I%A$ %A$ %IA$ %IIA andGroup-%IIIA constitute p-block.
(c) The elements haing their alence electrons ind-sub shell are called d-block elements. Tenertical columns in bet"een s-block and p-block of periodic table i.e. Group-I* to %III*constitute d-block.
(d) The elements haing their alence electrons inf-sub shell are called f-block elements. T"ohori,ontal ro"s on the bottom of periodic tablei.e. anthanides and Actinides series constitutef-block.
The elements of d-block and f-block are calledtransition elements. The d-block elements arecalled outer transition elements "hile f-blockelements are called inner transition elements.Their groups are called *-groups./n other hand elements of s-block and p-blockare called representatie elements. Their
groups are called A-groups.(iii) Metals and 0on-metals+
In the periodic table a diagonal line separatesmetals and non-metals. The elements on leftside of this line are metals "hile those presenton right side of the line are non-metals.
(i) &eriods+
The hori,ontal ro"s in the periodic table arecalled periods. In a period a shell starts fromthe first member and completes at the lastmember of the period. There are seenperiods in the periodic table.
&eriod-I+ It is the shortest period. Itconsists of only t"o elements both arerepresentatie elements and belong to s-block.
&eriod II 1 III+ These are short periods. Eachconsists of eight elements t"o from s-blockand si# from p-block.
&eriod I% 1 %+ These are long periods. Eachconsists of eighteen elements out of "hicheight representatie and ten transitionelements. /ut of eight representatie elements
t"o belongs to s-block and si# to p-block.2here as all the ten transition elements belongto d-block.
&eriod %I+ It is longest period. It consists of Thirty t"o elements$ out of "hich eightrepresentatie and t"enty four transitionelements. /ut of eight representatie elementst"o belongs to s-block and si# to p-block. /ut
of t"enty four transition elements ten belong tod-block "hile fourteen belong to f-block (i.e.anthanides).
&eriod %II+ It is incomplete period. It is alsolong period. Actinides are also member of thisperiod.
() Groups+The ertical columns in the periodic table arecalled groups or families. In a group allmembers hae same number of electrons intheir alence shell3 ho"eer their number of shells is different. There are eight groups in theperiodic table$ each group consists of t"o sub
groups A and *.
!ome of important groups are
Group-IA+ It consists of i$ 0a$ 4$ b$ 5sand 6r and is also called Alkali metal group.
Group-IIA+ It consists of *e$ Mg$ 5a$ !r$ *a
and a and is also called Alkaline Earth metalgroup.
Group-%IIA+ It consists of 6$ 5l$ *r$ I and Atand is also called 7alogen group.
Group %IIIA+ It consists of 7e$ 0e$ Ar 4r$ 8eand n. It is also called 9ero group$ Inertgases$ 0oble gases group.
Group-I*+ It consists of 5u$ Ag and Au andis also called 5oin age metals group.
Group-%III*+ It consists of three ertical
column or three triads.6e 5o 0iu h &d/s Ir &t
(i) anthanides and actinides+
6ourteen elements that follo" anthanum are
called anthanide "hile fourteen elements thatfollo" Actinium are called Actinide. Theybelong to f-block and are present in t"ohori,ontal ro"s at the bottom of periodic table.They are inner transition elements.
Periodicity in Physical Properties+
&roperties ary "ith increasing atomic number but arerepeated after regular interals and this is calledperiodicity in properties. &eriodicity occurs inproperties due to periodic ariation in electronicconfigurations.
Electronic Configuration:
The third period contains eight elements+ sodium$magnesium$ aluminium$ silicon$ phosphorus$ sulfur$chlorine$ and argon. The first t"o$ sodium andmagnesium$ are members of the s-block of the
periodic table$ "hile the others are members of the p-
block
Cheical eleent Cheical
!erie!
Electron
configuration
Na !odium Alkali
metal
:0e; <s
= Mg Magnesium Alkalineearthmetal
:0e; <s=
< "l Aluminium &ost-
transitionmetal
:0e; <s= <p
> Si !ilicon Metalloid :0e; <s=
<p=
? P &hosphorus &olyatomic
nonmetal
:0e; <s= <p<
@ S !ulfur &olyatomic
nonmetal
:0e; <s= <p>
Cl 5hlorine Biatomic
nonmetal
:0e; <s= <p?
C "r Argon 0oble gas :0e; <s= <p@
() "toic #a$ii+
It is difficult to state e#act atomic si,e as atom has nofi#ed boundaries also it is difficult to isolate atom.Therefore$ atomic radius is defined as Dhalf of the
• the number of protons in the nucleus increases so ...•
the nuclear charge increases ...• there are more electrons$ but the increase in shieldingis negligible because each e#tra electron enters thesame principal energy leel ...
• therefore the force of attraction bet"een the nucleusand the electrons increases ...
• so the atomic radius decreases.
As the number of electrons in each atom increases goingacross &eriod <$ you might e#pect the atomic radius toincrease. This does not happen$ because the number of protons also increases and there is relatiely little e#trashielding from electrons in the same principal energy leel.
(=)onic #a$ii
+DThe distance of place of ma#imum probability of outer most shell from the nucleus of an ion is called ionicradius.
The ionic radius of cation is much smaller than atomicradius of the element "hile ionic radius of anion is
much larger than atomic radius of the element.Buring formation of cation loss of outer shell occursand also hold of nucleus increases on remainingelectrons so cation is much smaller than neutral atom./n other hand in anion due to addition of e#traelectron(s) repulsion increases among electrons sothe electronic cloud e#pands and thus si,e of anionbecome larger than neutral atom.
&eriodicity in ionic radii occurs "ithin the same period.Elements on the left of a period forms cation so their si,e is smaller$ further$ across the period positie
charge increases so ionic radii decrease. Elements onthe right of a period forms anion so si,e increases andthen across the period Fe charge decreases so si,edecreases.
I II III % %I %II
&eriod-< 0a
Mg=
Al<
&-<
!-=
5l-
Ionic radius H? @? ? == C> C(in pm)
In group from top to bottom ionic radii increase.
(<) Melting an$ Boiling Point!+
&eriodicity in melting and boiling points occurs "ithinthe same period. Moing from group I to group I%melting and boiling point increase then moing fromgroup % to group %III they decrease as number of binding first increase and then decrease.
Bo"n the group in metals$ melting and boiling pointsdecrease "hile in non-metals increase.
(>) Metallic Character 'Electro-po!iti(it)*+The electron giing ability of an element is calledmetallic character or electro-positiity.
Across the period from left to right electro-positiitydecreases due to increasing nuclear charge. 2hiledo"n the group it increases due to increasing atomicsi,es.
(?) Electronegati(it)+
The electron puling ability of an element is calledelectronegatiity.
Across the period from left to right electronegatiityincreases due to increasing nuclear charge. 2hiledo"n the group it decreases due to increasing atomicsi,es.0a Mg Al !i & ! 5l Ar .H< .< .C =.= =.H =.?C <.@ --
It should be kept in mind that Ar has not assign anyE.0 alue as Ar does not form any coalent bond.
(@) oni+ation Energ),Potential+
DThe energy reuired to remoe the most looselybound electron from an isolated atom (gaseous atom) tomake cation is called Ioni,ation &otential or Ioni,ationEnergy.
This is an endothermic process in "hich energy is absorbedso sign for this energy is e. This energy is reuired tooercome the force of attraction of nucleus on the electron.
After remoal of first electron hold of nucleus on remainingelectrons increases so !econd I.& is greater than 6irst I.&because more energy is reuired to remoe the secondelectron and so on.
e.g (i) 0a J 0a
e
-
(I.E) K >H@ kLmol(=$C$) (=$C)
e.g (i) Mg J Mg
e- (I.E) K <C kLmol
(=$C$=) (=$C$)
Mg
J Mg=
e-
(I.E)= K >? kLmol(=$C$) (=$C)
Trend in Periodic Table+Generally I.E increase in a period from left to right dueto decreasing atomic si,e and increasing nuclear charge. *ut anomalies are obsered at group A$ IIAand %IIIA they hae e#tra ordinary high I.E. This is due
to the reason that they hae completely filled or half filled outer orbitals "hich are more stable and thustheir electrons are difficult to remoe so their I.E arehigh.
e.g. trend of =nd period isGroups IA IIA IIIA I%A %A %IA %IIA %IIIAElements i *e * 5 0 / 6 0eI.E ?= H C C@ >= <> @C =C
/n other hand in a group I.E decrease from top tobottom due to increasing atomic si,e.
()Elec
tron "ffinit)+
DThe energy released ("ith fe" e#ception) "hen anelectron is added to the outer most shell of an isolated(gaseous atom) to make anion is called Electron Affinity.
st electron affinities are energy released so they hae Fealues. *ut second electron affinities are energy absorbed sohae e alues.
2hen first electron is added to an isolated atom$ nucleusproides attraction for this additional electron so energy isreleased. *ut "hen second electron is added then energy isreuired to oercome repulsion bet"een anion and electronso energy is absorbed. In case of groups IIA$ %A and %IIIAeen first electron affinities hae e alues.
• The modern &eriodic Table is arranged in order of increasing atomic number. As one moes from oneelement to another on the right$ one more proton isfound in the nucleus$ and one more electron is foundin the same electron NshellN (energy leel). 6or thisreason$ all the elements in &eriod < hae the first
electron NshellN (energy leel) filled "ith = electrons andthe second electron NshellN (energy leel) filled "ith Celectrons (the electronic configuration of 0eon).!odium begins a ne" electron NshellN ( <rdenergy leel)"ith electron$ Magnesium has = electrons in thethird electron NshellN (energy leel)$ Aluminium has <electrons in the third electron NshellN (energy leel) etc$until finally the third electron NshellN (energy leel) is
filled "ith C electrons and the stable electronicconfiguration of the 0oble Gas Argon is reached(=$C$C).
• Atomic radius of the elements decrease across the&eriod from left to right. As "e moe from left to rightacross the period one more proton is added to thenucleus of each successie atom$ and one moreelectron is added to the same electron NshellN (energyleel) of each successie atom. The increasedpositie charge in the nucleus of each successieatom attracts all the electrons in the atom morestrongly$ so they are dra"n in more closely to"ardsthe nucleus.
• st Ioni,ation Energy (the energy reuired to remoean electron from the gaseous atom) increases across
the &eriod from left to right. The further a"ay from thepositiely charged nucleus that a negatiely chargedelectron is$ the less strongly the electron is attracted tothe nucleus and so the more easily that electron canbe remoed. !o$ as the atomic radius decreases from
left to right across the &eriod so the st Ioni,ationEnergy increases.
• Electronegatiity (the relatie tendency sho"n by anatom to attract electrons to itself) increases across the&eriod from left to right. Typically$ metals hae lo"electronegatiity$ little ability to attract electrons$ "hilenon-metals hae high electronegatiity$ greater abilityto attract electrons. As "e moe from left to rightacross the &eriod$ the elements become less metallic
in nature (more non-metallic).• In general metals are hard (E85E&T Group (IA)metals "hich are uite soft)$ hae metallic lustre$ highmelting and boiling points (E#cept for mercury "hich isa liuid at room temperature$ and the Group (IA)metals "hich hae lo" meltingboiling pointscompared to other metals) and good electricalconductiity. In general$ non-metals are dull$ brittle$
hae lo" melting and boiling points and are electricalinsulators (non-conductors of electricity). Elements tothe left of &eriod < e#hibit metallic properties$elements to the right sho" non-metallic properties.!ilicon is a semi-metal (metalloid).
Propertie! of O.i$e! an$ Chlori$e! of Perio$ 3 Eleent!
Element Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine
Chloride formula
)ide formula
NaCl
Na2O
MgCl2
MgO
lCl3!
l2O3
"iCl4
"iO2
#Cl3
#4O6
"Cl2
"O2
Cl2
Cl2O7
Chloride melting point ( oC
)ide melting point ( oC
801920
7122800
1932045
-681700
-92420
-8017
-101-92
Chloride bonding
)ide bonding
$oni%
$oni%
$oni%
$oni%
Co&alent
$oni%
Co&alent
Co&alent
Co&alent
Co&alent
Co&alent
Co&alent
Co&alent
Co&alent
Chloride conducti&ity of li*uid
)ide conducti&ity of li*uid
ood
ood
ood
ood
#oo
ood
Nil
Nil
Nil
Nil
Nil
Nil
Nil
Nil
Chloride acid+base beha&iour
)ide acid+base beha&iour
Ne*tal
+asi%
Ne*tal
+asi%
%idi%
motei%
%idi%
%idi%
%idi%
%idi%
%idi%
%idi%
%idi%
%idi%
Aluminium forms a coalent anydrous aluminium chloride$ Al=5l@$ "hich forms ions in aueous solution. Ionic aluminiumchloride$ Al5l<.@7=/$ can be crystallised out of this solution.
!odium has a ery e#othermic reaction "ith cold "ater producing hydrogen and a colourless solution of sodiumhydro#ide.
Magne!iu
Magnesium has a ery slight reaction "ith cold "ater$ butburns in steam.
A ery clean coil of magnesium dropped into cold "ater eentually gets coered in small bubbles of hydrogen "hichfloat it to the surface. Magnesium hydro#ide is formed as aery thin layer on the magnesium and this tends to stop thereaction.
Magnesium burns in steam "ith its typical "hite flame toproduce "hite magnesium o#ide and hydrogen.
"luiniu
Aluminium po"der heated in steam produces hydrogen andaluminium o#ide. The reaction is relatiely slo" because of the e#isting strong aluminium o#ide layer on the metal$ andthe build-up of een more o#ide during the reaction.
There is a fair amount of disagreement in the books and onthe "eb about "hat silicon does "ith "ater or steam. Thetruth seems to depend on the precise form of silicon you areusing.
The common shiny grey lumps of silicon "ith a rather metal-like appearance are fairly unreactie. Most sources suggest
that this form of silicon "ill react "ith steam at red heat toproduce silicon dio#ide and hydrogen.
*ut it is also possible to make much more reactie forms of silicon "hich "ill react "ith cold "ater to gie the sameproducts. Pho!phoru! an$ !ulphur
These hae no reaction "ith "ater.
Chlorine
5hlorine dissoles in "ater to some e#tent to gie a greensolution. A reersible reaction takes place to produce a
mi#ture of hydrochloric acid and chloric(I) acid (hypochlorousacid).
In the presence of sunlight$ the chloric(I) acid slo"ly decomposes to producemore hydrochloric acid$ releasing o#ygen gas$ and you maycome across an euation sho"ing the oerall change+
2hite phosphorus catches fire spontaneously in air$ burning"ith a "hite flame and producing clouds of "hite smoke - ami#ture of phosphorus(III) o#ide and phosphorus(%) o#ide.
The proportions of these depend on the amount of o#ygenaailable. In an e#cess of o#ygen$ the product "ill be almostentirely phosphorus(%) o#ide.
6or the phosphorus(III) o#ide+
6or the phosphorus(%) o#ide+
Sulphur
!ulphur burns in air or o#ygen on gentle heating "ith a paleblue flame. It produces colourless sulphur dio#ide gas.
Magnesium burns "ith its usual intense "hite flame to gie"hite magnesium chloride.
"luiniu
Aluminium is often reacted "ith chlorine by passing drychlorine oer aluminium foil heated in a long tube. Thealuminium burns in the stream of chlorine to produce erypale yello" aluminium chloride. This sublimes (turns straightfrom solid to apour and back again) and collects further do"n the tube "here it is cooler.
Silicon
If chlorine is passed oer silicon po"der heated in a tube$ itreacts to produce silicon tetrachloride. This is a colourless
liuid "hich aporises and can be condensed further alongthe apparatus.
Pho!phoru!
2hite phosphorus burns in chlorine to produce a mi#ture of t"o chlorides$ phosphorus(III) chloride and phosphorus(%)chloride (phosphorus trichloride and phosphoruspentachloride).
&hosphorus(III) chloride is a colourless fuming liuid.
The trend in acid-base behaiour is sho"n in ariousreactions$ but as a simple summary+
• The trend is from strongly basic o#ides on the left-hand side to strongly acidic ones on the right$ ia anamphoteric o#ide (aluminium o#ide) in the middle. Anamphoteric o#ide is one "hich sho"s both acidic andbasic properties.
6or this simple trend$ you hae to be looking only at thehighest o#ides of the indiidual elements. Those are the oneson the top ro" aboe$ and are "here the element is in its
highest possible o#idation state. The pattern isnNt so simple if you include the other o#ides as "ell.
6or the non-metal o#ides$ their acidity is usually thought of interms of the acidic solutions formed "hen they react "ith"ater - for e#ample$ sulphur trio#ide reacting to gie sulphuricacid. They "ill$ ho"eer$ all react "ith bases such as sodiumhydro#ide to form salts such as sodium sulphate.
These reactions are all e#plored in detail on the rest of thispage.
Chei!tr) of the in$i(i$ual o.i$e!
So$iu o.i$e
!odium o#ide is a simple strongly basic o#ide. It is basicbecause it contains the o#ide ion$ /=-$ "hich is a ery strongbase "ith a high tendency to combine "ith hydrogen ions.
Bepending on its concentration$ this "ill hae a p7 around>.
As a strong base$ sodium o#ide also reacts "ith acids$ it"ould react "ith dilute hydrochloric acid to produce sodiumchloride solution.
Magne!iu o.i$e
Magnesium o#ide is again a simple basic o#ide$ because italso contains o#ide ions. 7o"eer$ it isnNt as strongly basic assodium o#ide because the o#ide ions arenNt so free.
In the sodium o#ide case$ the solid is held together byattractions bet"een and =- ions. In the magnesium o#idecase$ the attractions are bet"een = and =-. It takes moreenergy to break these.
7o"eer$ if you test the p7 of the liuid$ you find that it issome"here around p7 H - sho"ing that it is slightly alkaline.
it reacts "ith "arm dilute hydrochloric acid to gie magnesiumchloride solution.
"luiniu o.i$e
Aluminium o#ide is amphoteric . It has reactions as both abase and an acid.
Aluminium o#ide doesnNt react in a simple "ay "ith "ater inthe sense that sodium o#ide and magnesium o#ide do$ anddoesnNt dissole in it. Although it still contains o#ide ions$ theyare held too strongly in the solid lattice to react "ith the "ater.
!ilicon dio#ide has no basic properties - it doesnNt containo#ide ions and it doesnNt react "ith acids. Instead$ it is ery"eakly acidic$ reacting "ith strong bases.
!ilicon dio#ide doesnNt react "ith "ater$ because of the
difficulty of breaking up the giant coalent structure.
!ilicon dio#ide reacts "ith sodium hydro#ide solution$ but onlyif it is hot and concentrated. A colourless solution of sodiumsilicate is formed.
In *last 6urnace e#traction of iron - in "hich calcium o#ide(from the limestone "hich is one of the ra" materials) reacts"ith silicon dio#ide to produce a liuid slag$ calcium silicate.This is also an e#ample of the acidic silicon dio#ide reacting"ith a base.
The pho!phoru! o.i$e!
phosphorus(III) o#ide$ &>/@$ and phosphorus(%) o#ide$ &>/.
Phosphorus(III) oxide
&hosphorus(III) o#ide reacts "ith cold "ater to gie a solutionof the "eak acid$ 7<&/< - kno"n ariously as phosphorousacid$ orthophosphorous acid or phosphonic acid. Its reaction"ith hot "ater is much more complicated.
&hosphorous acid has a p4a of =. "hichmakes it stronger than common organic acidslike ethanoic acid (p4a K >.@).
sodium hydro#ide solution depending on the proportionsused.
In the first case$ only one of the acidic hydrogens has reacted"ith the hydro#ide ions from the base. In the second case(using t"ice as much sodium hydro#ide)$ both hae reacted.
If you "ere to react phosphorus(III) o#ide directly "ith sodiumhydro#ide solution rather than making the acid first$ you "ouldend up "ith the same possible salts.
Phosphorus(V) oxide&hosphorus(%) o#ide reacts iolently "ith "ater togie a solution containing a mi#ture of acids$ thenature of "hich depends on the conditions. 2eusually Pust consider one of these$ phosphoric(%) acid$7<&/> - also kno"n Pust as phosphoric acid or asorthophosphoric acid.
This time the pure un-ionised acid has the structure+
&hosphoric(%) acid is also a "eak acid"ith a p4a of =.?. That makesit fractionally "eaker than phosphorousacid. !olutions of both of these acids of concentrations around mol dm-< "ill
hae a p7 of about .
The !ulphur o.i$e!
Sulphur dioxide
!ulphur dio#ide is fairly soluble in "ater$ reacting "ith it togie a solution of sulphurous acid (sulphuric(I%) acid)$ 7=!/<.This only e#ists in solution$ and any attempt to isolate it Pustcauses sulphur dio#ide to be gien off again.
!ulphur dio#ide "ill also react directly "ith bases such assodium hydro#ide solution
Sulphur trioxide
!ulphur trio#ide reacts iolently "ith "ater to produce a fog of concentrated sulphuric acid droplets.
The acid reacts "ith "ater to gie a hydro#onium ion(a hydrogen ion in solution$ if you like) and ahydrogensulphate ion. This reaction is irtually Qcomplete.
The second hydrogen is more difficult to remoe. Infact the hydrogensulphate ion is a relatiely "eak acid
- similar in strength to the acids "e hae alreadydiscussed on this page. This time you get aneuilibrium+
!ulphuric acid$ of course$ has all the reactions of a strongacid that you are familiar "ith from introductory chemistrycourses. 6or e#ample$ the normal reaction "ith sodiumhydro#ide solution is to form sodium sulphate solution - in"hich both of the acidic hydrogens react "ith hydro#ide ions.
Chlorine(VII) oxide
5hlorine(%II) o#ide is the highest o#ide of chlorine - thechlorine is in its ma#imum o#idation state of . It continuesthe trend of the highest o#ides of the &eriod < elementsto"ards being stronger acids.
5hlorine(%II) o#ide reacts "ith "ater to gie the ery strongacid$ chloric(%II) acid - also kno"n as perchloric acid. The p7of typical solutions "ill$ like sulphuric acid$ be around .
5hloric(%II) acid reacts "ith sodium hydro#ide solution to forma solution of sodium chlorate(%II).
5hlorine(%II) o#ide itself also reacts "ith sodium hydro#idesolution to gie the same product.
Chlorine(I) oxide
5hlorine(I) o#ide is far less acidic than chlorine(%II) o#ide. Itreacts "ith "ater to some e#tent to gie chloric(I) acid$ 7/5l -also kno"n as hypochlorous acid.
5hloric(I) acid reacts "ith sodium hydro#ide solutionto gie a solution of sodium chlorate(I) (sodiumhypochlorite).
5hlorine(I) o#ide also reacts directly "ith sodiumhydro#ide to gie the same product.
"toic #a$ii+It is difficult to state e#act atomic si,e as atom has nofi#ed boundaries also it is difficult to isolate atom.Therefore$ atomic radius is defined as Dhalf of thedistance bet"een nuclei of t"o identical atomsbonded together through single coalent bond.
Atomic radii decrease in a period from left to right dueto increasing nuclear charge and increase in a groupfrom top to bottom due to addition of ne" shells.
Melting an$ Boiling Point!+&eriodicity in melting and boiling points occurs "ithin thesame period. Moing from group I to group I% melting and
boiling point increase then moing from group % to group %IIIthey decrease as number of binding first increase and thendecrease.
Bo"n the group in metals$ melting and boiling pointsdecrease "hile in non-metals increase.
Metallic Character 'Electropo!iti(it)*+
The electron giing ability of an element is called metalliccharacter or electropositiity.
Across the period from left to right electropositiity decreasesdue to increasing nuclear charge. 2hile do"n the group itincreases due to increasing atomic si,es.
Electronegati(it)+
The electron puling ability of an element is calledelectronegatiity.
Across the period from left to right electronegatiity increases
due to increasing nuclear charge. 2hile do"n the group itdecreases due to increasing atomic si,es.
#eaction! of "l6ali Metal /ith Chlorine
All of the alkali metals react igorously "ith chlorine gas.Each reaction produces a "hite crystalline salt. The reactiongets more iolent as you moe do"n Group $ sho"ing ho"
reactiity increases do"n the group.
Lithiu
If a piece of hot lithium is lo"ered into a Par of chlorine$ "hitepo"der is produced and settles on the sides of the Par. This isthe salt lithiu chlori$e.
lithiu 7 chlorine 8 lithiu chlori$e
9Li'!* 7 Cl9'g* 8 9LiCl'!*
So$iu
If a piece of hot sodium is lo"ered into a Par of chlorine$ thesodium burns "ith a bright yello" flame. 5louds of "hitepo"der are produced and settle on the sides of the Par. This is
the salt!o$iu chlori$e
.The reaction of sodium "ith chlorine is similar to the reaction"ith lithium$ but more igorous.
Most carbonates tend to decompose on heating to gie themetal o#ide and carbon dio#de.
6or e#ample$ a typical Group 2 carbonate like calciumcarbonate decomposes like this+
In Group 1$ lithium carbonate behaes in the same "ay -
producing lithium o#ide and carbon dio#ide.
The rest of the Group carbonates donNt decompose at*unsen temperatures$ although at higher temperatures they"ill. The decomposition temperatures again increase as yougo do"n the Group.
he thermal stability o! the hydrogencarbonates
The Group 2 hydrogencarbonates like calciumhydrogencarbonate are so unstable to heat that they onlye#ist in solution. Any attempt to get them out of solutioncauses them to decompose to gie the carbonate$ carbon
dio#ide and "ater.
*y contrast$ the Group 1 hydrogencarbonates are stableenough to e#ist as solids$ although they do decompose easilyon heating. 6or e#ample$ for sodium hydrogencarbonate+
he thermal stability o! the hydrogencarbonates
The Group 2 hydrogencarbonates like calciumhydrogencarbonate are so unstable to heat that they only
e#ist in solution. Any attempt to get them out of solutioncauses them to decompose to gie the carbonate$ carbondio#ide and "ater.
*y contrast$ the Group 1 hydrogencarbonates are stableenough to e#ist as solids$ although they do decompose easilyon heating. 6or e#ample$ for sodium hydrogencarbonate+
"xplaining the trend in terms o! the polarising ability o! the positi#e ion
A small positie ion has a lot of charge packed into a smallolume of space - especially if it has more than one positiecharge. It has a high charge density and "ill hae a markeddistorting effect on any negatie ions "hich happen to benear it.
A bigger positie ion has the same charge spread oer alarger olume of space. Its charge density "ill be lo"er$ and it"ill cause less distortion to nearby negatie ions.
If you "orked out the structure of a carbonate ion using Rdots-and-crossesR or some similar method$ you "ould probablycome up "ith+
This sho"s t"o single carbon-o#ygen bondsand one double one$ "ith t"o of the o#ygenseach carrying a negatie charge.'nfortunately$ in real carbonate ions all the bonds areidentical$ and the charges are spread out oer the "hole ion -
although concentrated on the o#ygen atoms. 2e say that thecharges are delocalized .
This is a rather more complicated ersion of the bonding youmight hae come across in ben,ene or in ions like ethanoate.6or the purposes of this topic$ you donNt need to understandho" this bonding has come about.
Polarising the carbonate ion
0o" imagine "hat happens "hen this ion is placed ne#t to apositie ion. The positie ion attracts the delocalised electronsin the carbonate ion to"ards itself. The carbonate ionbecomes polarised. The diagram sho"s "hat happens "ithan ion from Group =$ carrying t"o positie charges
4lae Te!t
6lame tests are used to identify the presence of a relatielysmall number of metal ions in a compound. 0ot all metal ionsgie flame colors. 6or Group compounds$ flame tests areusually by far the easiest "ay of identifying "hich metal youhae got. 6or other metals$ there are usually other easy
methods "hich are more reliable - but the flame test can gie
a useful hint as to "here to look.
Practical $etail! in carr)ing out a flae te!t
• 5lean a platinum or nichrome (a nickel-chromiumalloy) "ire by dipping it into concentrated hydrochloric acidand then holding it in a hot *unsen flame. epeat this untilthe "ire produces no color in the flame.
• 2hen the "ire is clean$ moisten it again in the acidand then dip it into a small amount of the solid to be tested sothat some sticks to the "ire. &lace the "ire back in the flame.
•
If the flame color is "eak$ it is often helpful to dip the"ire back in the acid and put it back into the flame as if cleaning it. This should produce a ery short but intense flashof color.
The color!
The table belo" gies a rough color guide for the elements. As people see and describe colors differently$ it is impossibleto proide a definitie guide.
If a red flame is produced$ the flame test must be repeated"ith kno"n samples of lithium$ strontium$ etc$ comparing thecolors of the unkno"n and the samples.
%roup -" Eleent! ' "l6aline Earth Metal!*+
Electronic 5onfiguration
"l6aline Earth Metal!
>*e s=$ =s= :7e;=s=
=Mg s=$ =s=$ =p@$ <s= :0e;<s=
=5a s=$ =s=$ =p@$ <s=$ <p@$ >s= :Ar;>s=
<C!r
s
=
$ =s
=
$ =p
@
$ <s
=
$ <p
@
$ >s
=
$ <d
$>p@$ ?s= :4r;?s
=
?@*a s=$ =s=$ =p@$ <s=$ <p@$ >s=$ <d$
>p@$ ?s=$ >d$ ?p@$ @s=:8e;@s=
CCa s=$ =s=$ =p@$ <s=$ <p@$ >s=$ <d$
>p@$ ?s=$ >d$ ?p@$ @s=$ >f >$
?d$ @p@$ s=
:n;s=
*eryllium+ The principal ore of beryllium is analuminosilicate ore *eryl :*e< Al=(!i/<)@;
Magnesium+ It is ery abundant in rocks of earthSs crust. It isfound in sea "ater and springs "ater. Itsmineral are Bolomite (Mg5/<.5a5/<)$Magnesite (Mg5/<)$ Epsom salt(Mg!/>.7=/)$ !oap stone (Talc):Mg=(!i=/?)=.Mg(/7)=;$ and Asbestos:5aMg<(!i/<)>;.
5alcium+ It is ery abundant in rocks of earthSs crust. It
is present in sea shells. Its important mineralare 5alcite or ime stone or Marble (5a5/<)$Gypsum (5a!/>.=7=/).
!trontium+ Its important ore is !trontianite (!r5/<).
*arium+ Its important ore is *arite (*a!/>).
adium+ It is radioactie and is of great importance. It is
found in all uranium ores but in lo"concentration$ as product of radioactie decay.
%eneral Ph)!ical Propertie! of "l6aline earth etal!(group IIA)+
(i) They are harder than alkali metals.
*eryllium is hard enough to scratch glass.(ii) They are grayish "hite colour metals.(iii) They are malleable.(i) Their melting and boiling points are higher
than alkali metals.() They gie characteristic colours to *unsen
burner flame.5a K *rick red !r K 5rimson red *a K
Green a K 5rimson red%eneral Cheical Propertie! of "l6ali etal! an$ "l6aline
(i) Bue to lo" ioni,ation energies both alkali andalkaline earth metals are reactie and they formionic compounds.
(ii) /#idation state of alkali metals in their compoundsis "hile that of alkaline earth metals is =.
(iii) They hae strong reducing ability and this abilityincreases do"n the group.
(i&) Reaction with Oxygen+ They react readily "itho#ygen and produce their o#ides.
ithium forms normal o#ide>i /= J =i=/!odium forms pero#ide
=0a /= J 0a=/=
4$ b 1 5s forms super o#ide4 /= J 4/=
Alkaline earth metals form normal o#ides=5a /= J =5a/
(&) Reaction with Hydrogen+ All s-block elementse#cept *e react directly "ith hydrogen to formhydride. The hydrides are ionic e#cept *e7= andMg7= these t"o are coalent.
=0a 7= J =0a75a 7= J 5a7=
(&i) Reaction with Chlorine+ All s-blockelements react directly "ith chlorine to produce
chlorides. All their chlorides are ionic ho"eer *e5l= is coalent Mg5l= is intermediate.=0a 5l= J =0a5l5a 5l= J 5a5l=
(&ii) Reaction with Water + Alkali metals reactigorously "ith "ater to produce their hydro#ideand liberate hydrogen. eaction is highlye#othermic so the hydrogen produced catches fire.
%igorousness of reaction increases do"n thegroup.
*eryllium does not react "ith "ater een atstrong heating$ Magnesium react "ithboiling "ater the rest react "ith cold "ater.
(&iii) Reaction with Nitrogen+ Alkali metals donot react "ith nitrogen /nly ithium reacts "ithnitrogen ho"eer all alkaline earth metals react"ith nitrogen on heating and produce their nitrides.
@i 0= J =i<0<Mg 0= J Mg<0=
(i) Reaction with Carbon+ Alkali metals donot react "ith carbon /nly ithium reacts "ithcarbon ho"eer all alkaline earth metals react "ithcarbon on heating and produce their carbides.
>i 5 J i>5>Mg =5 J Mg>5=
() Reaction with Sulphur + Alkali and Alkaline earth metals react "ith molten sulphur toproduce sulphides.
=0a ! J 0a=!Mg ! J Mg!)$ro.i$e!+
7ydro#ides are produced either by reaction of metals"ith "ater or metal o#ide "ith "ater.=0a =7=/ J =0a/7 7=
5a/ 7=/ J 5a(/7)=
=0a=/= =7=/ J >0a/7 =/=
• 7ydro#ides of both groups are ionic and are "hitecrystalline solids.
• !olubility of hydro#ides in "ater increases do"n thegroup. Among alkali metals$ i/7 is sparingly solublein "ater$ the rest are soluble. Among alkaline earthmetals *e(/7)= is insoluble$ Mg(/7)= forms
alkaline earth metals as "ell as that of lithium areinsoluble.
• 5arbonates of alkali metals are stable e#cept that of ithium$ "hile that of alkaline earth metals decomposeon heating. Ease of decomposition of carbonatesdecreases do"n the group. !maller is the metal ionmore is the lattice energy of the resulting metal o#ideand hence higher the stability of the o#ide and ice
ersa.i=5/< J i=/ 5/=
5a5/< J 5a/ 5/=
• 5arbonates of alkali metals are hydroly,ed by "ater toproduce alkalis.
0a=5/< =7=/ J =0a/7 7=5/<
• !ome Important carbonates+
0a=5/<+ It is an important industrial chemical. Itshydrated form i.e. 0a=5/<.7=/ is used as "ashingsoda in laundry "hile its anhydrous form i.e 0a=5/< iscalled !oda ash and is used in glass industry and
many more. At temperature belo" <?.=o5 it
crystalli,es as 0a=5/<.7=/ and is called "ashingsoda. It is efflorescent so loses "ater on standing inair and slo"ly conerts to 0a=5/<.7=/. In aueoussolution it hydrolyses by "ater to 0a/7.0a=5/< =7=/ J =0a/7 7=5/<
Mg5/<+ It is called magnesite. It on heatingdecomposes to gie Mg/ (Magnesia). Magnesia and
clay are mi#ed$ pressed and dried to make refractorybricks for furnace lining.
5a5/<+ It is called lime stone$ marble and alsocalled calcite. It on strong heating decomposes to gie
5a/ (uick lime).uick lime is used for cement andglass industries.
(>) Bicaronate!+
*icarbonates are produced by passing 5arbon dio#idethrough solution or suspension of metal carbonates.
0a=5/< 7=/ 5/= J =0a75/<
5a5/< 7=/ 5/= J 5a(75/<)=
•
*icarbonates of alkali metals are sparingly soluble in"ater "hile that of alkaline earth metals are soluble in"ater.
• *icarbonates of alkali metals are stable at roomtemperature ho"eer they decompose on heating. /nthe other hand bicarbonates of alkaline earth metalsare unstable een at room temperature$ thus they
cannot be isolated from solution.=0a75/< 7eating 0a=5/<
7=/ 5/=
5a(75/<)= 5a5/< 7=/ 5/=
• !odium bicarbonate is baking soda and is source of carbon dio#ide in baking process as "ell as in firee#tinguishers.
Nitrate!+
0itrates are produced by neutrali,ation of metalo#ides or metal hydro#ides "ith nitric acid.
0a/7 70/< J 0a0/< 7=/•
0itrates of both groups are colorless$ soluble$ neutralcrystalline salts.• 0itrates of alkali metals e#cept lithium on heating
decompose to gie metal nitrite "hile nitrates of lithium and alkaline earth metals gie metal o#ide.
*eryllium being st member of the family sho"s somedifferences "ith rest of the members of its family.
(i) *eryllium atom is ery small so according to
6aPanSs rule "hich states that small highly chargedcations tend to form polar coalent compoundsthus its compounds are some "hat coalent.
(ii) It is as hard as iron "hile other members of thefamily are soft.
(iii) Melting and boiling point of *eryllium are muchhigher than other members of its family.
(i) 7alides of *eryllium are soluble in organic
solents "hile that of other are soluble in "ater.() /#ide of *eryllium is amphoteric "hile that of others are basic in nature.
(i) It is the only member of the family "hich onreaction "ith alkalies liberate hydrogen.
*e =0a/7 J 0a=*e/= 7=
(&age->)
(ii) *eryllium is resistant to complete o#idation due toits *e/ coating.
h) BeCl9 i! co(alent not onic;
The polarising po"er of beryllium is high and the polarisabilityof chlorine is high so beryllium essentially pulls the donatedelectrons back so they are effectiely shared. *eryllium is a
small atom and forms a = charge so it has a highelectronegatiity alue$ and chlorine is fairly large "ith a lo"charge (-) so electrons are easily pulled a"ay from it.
*eryllium has uite a high electronegatiity compared "ith therest of the Group. That means that it attracts a bonding pair of electrons to"ards itself more strongly than magnesium andthe rest do. In order for an ionic bond to form$ the berylliumhas to let go of its electrons. It is too electronegatie to dothat
*ut it also reacts "ith bases such as sodium hydro#idesolution. *eryllium hydro#ide reacts "ith the sodiumhydro#ide to gie a colourless solution of sodiumtetrahydro#oberyllate.
This contains the comple# ion$ :*e(/7)>;=-. The namedescribes this ion. Tetra means four3 hydroxo refers to the /7groups3beryllate sho"s that the beryllium is present in a
negatie ion. The RateR ending al"ays sho"s that the ion isnegatie.
%roup 2-" Eleent!:
This group consists of metals and non metals. 5arbon and!ilicon are non-metals "hile other are metals. The electronicconfiguration of group I%-A is+
This means that it is slightly more difficult to remoe the pelectrons from lead than from tin. The reasons for all this lie inthe Theory of elatiity. 2ith the heaier elements like lead$there is "hat is kno"n as a relati#istic contraction of theelectrons "hich tends to dra" the electrons closer to thenucleus than you "ould e#pect. *ecause they are closer tothe nucleus$ they are more difficult to remoe. The heaier theelement$ the greater this effect.
This affects s electrons much more than p electrons.In the case of lead$ the relatiistic contraction makes itenergetically more difficult to remoe the @s electrons thanyou might e#pect. The energy releasing terms "hen ions areformed (like lattice enthalpy or hydration enthalpy) obiouslyarenNt enough to compensate for this e#tra energy. Thatmeans that it doesnNt make energetic sense for lead to form
> ions.
The inert pair effect in the foration of co(alent on$!
Uou need to think about "hy carbon normally forms four coalent bonds rather than t"o.
'sing the electrons-in-bo#es notation$ the outer electronicstructure of carbon looks like this+
There are only t"o unpaired electrons. *efore carbon formsbonds$ though$ it normally promotes one of the s electrons tothe empty p orbital.
That leaes > unpaired electrons "hich (after hybridisation)can go on to form > coalent bonds.
It is "orth supplying the energy to promote the s electron$because the carbon can then form t"ice as many coalentbonds. Each coalent bond that forms releases energy$ andthis is more than enough to supply the energy needed for thepromotion.
/ne possible e#planation for the reluctance of lead to do thesame thing lies in falling bond energies as you go do"n the
Group. *ond energies tend to fall as atoms get bigger and thebonding pair is further from the t"o nuclei and better screened from them.
6or e#ample$ the energy released "hen t"o e#tra &b-8bonds ("here 8 is 7 or 5l or "hateer) are formed may nolonger be enough to compensate for the e#tra energy neededto promote a @s electron into the empty @p orbital.
This "ould "ould be made "orse$ of course$ if the energygap bet"een the @s and @p orbitals "as increased by therelatiistic contraction of the @s orbital.
by 4a,imier, 6aPans in H=<$ are used to predict "hether a chemical bond "ill be coalent or ionic$ and depend on thecharge on the cation and the relatie si,es of the cation
and anion. They can be summari,ed in the follo"ing table+
onic Co(alent
o" positie charge igh po!iti(e charge
arge cation Sall cation
!mall anion Large anion
TE CLO#0ES O4 C"#BON> SLCON "N0 LE"0
Caron> !ilicon an$ lea$ tetra-chlori$e!
These all hae the formula 85l>.
They are all simple coalent molecules "ith a typical
tetrahedral shape. All of them are liuids at roomtemperature. (Although at room temperature$ lead(I%) chloride"ill tend to decompose to gie lead(II) chloride and chlorinegas.
ead(II) chloride is a "hite solid$ melting at ?O5. It is eryslightly soluble in cold "ater$ but more soluble in hot "ater.Uou can think of lead(II) chloride as being mainly ionic incharacter.
Stailit)
At the top of Group >$ the most stable o#idation state sho"nby the elements is >. This is the o#idation state sho"n bycarbon and silicon in 55l> and !i5l>. These therefore hae notendency to split up to gie dichlorides.
7o"eer$ the relatie stability of the > o#idation state falls asyou go do"n the Group$ and the = o#idation state becomesthe most stable by the time you get to lead.
ead(I%) chloride decomposes at room temperature to giethe more stable lead(II) chloride and chlorine gas.
#eaction /ith /ater 'h)$rol)!i!*
Caron tetrachlori$e 'tetrachloroethane*
5arbon tetrachloride has no reaction "ith "ater. If you add itto "ater$ it simply forms a separate layer underneath the layer of "ater.
!uppose a "ater molecule is going to react "ith the carbontetrachloride. The reaction "ould hae to start by the "ater
moleculeNs o#ygen attaching itself to the carbon atom ia theo#ygenNs lone pair. A chlorine atom "ould get pushed off thecarbon in the process.
6irst$ the chlorines are so bulky and the carbon atom sosmall$ that the o#ygen canNt easily get at the carbon atom.
. . . and een if it did$ there "ill be a stage "here there isconsiderable cluttering around that carbon atom before thechlorine atom breaks a"ay completely. There is going to be alot of repulsion bet"een the arious lone pairs on all theatoms surrounding the carbon.
That cluttering is going to make this half-"ay stage (properly
called a Rtransition stateR) ery unstable. A ery unstabletransition state means a ery high actiation energy for thereaction.
The other problem is that there isnNt a conenient emptyorbital on the carbon that the o#ygen lone pair can attach to.
If it could attach before the chlorine starts to break a"ay$ that"ould be an adantage. 6orming a bond releases energy$and that energy "ould therefore be readily aailable for breaking a carbon-chlorine bond. *ut in the case of a carbonatom$ that isnNt possible.
Silicon tetrachlori$e
The situation is different "ith silicon tetrachloride.The silicon atom is bigger$ and so there is more room aroundit for the "ater molecule to attack$ and the transition state "illbe less cluttered.
*ut silicon has the additional adantage that there are empty<d orbitals aailable to accept a lone pair from the "ater molecule. 5arbon doesnNt hae =d orbitals because there areno such things. There are no empty =-leel orbitals aailablein the carbon case.
This means that the o#ygen can bond to the silicon before theneed to break a silicon-chlorine bond. This makes the "holeprocess energetically easier.
!o . . . silicon tetrachloride reacts iolently "ith "ater to gie"hite solid silicon dio#ide and steamy fumes of 75l.
iuid !i5l> fumes in moist air for this reason - it is reacting"ith "ater apour in the air.
Lea$ tetrachlori$e 'lea$'2* chlori$e*
The reaction of lead(I%) chloride "ith "ater is Pust like thesilicon tetrachloride one. Uou "ill get lead(I%) o#ide producedas a bro"n solid and fumes of hydrogen chloride gien off.(This "ill also$ of course$ be confused by the decomposition
of the lead(I%) chloride to gie lead(II) chloride and chlorinegas - see aboe.)
Lea$'* chlori$e
'nlike the tetrachlorides$ lead(II) chloride can be thought of
as ionic. It is sparingly soluble in cold "ater$ but more solublein hot "ater. ooked at simply$ solubility in "ater inoles thebreak-up of the ionic lattice and the hydration of the lead(II)and chloride ions to gie &b=
O.i$e! of Caron+!tructure of carbon dio#ide (5/=)+
It is most stable o#ide of carbon. It has linear structurehaing t"o carbon-o#ygen double coalent bonds.
The bond length is .?o A or .? # -. 5arbondio#ide molecule is non-polar due to its linear structure haing ,ero dipole moment.
/ V 5 V /
In solid state (i.e. dry ice) carbon dio#ide has face-centeredcubic structure. !tructure of carbon subo#ide (5</=)+
!tructure of carbon subo#ide is the resonance hybridof the follo"ing contributing structures.
/ V 5 V 5 V 5 V / W / ? 5 F 5 ? 5 F /- W -/ F 5 ? 5 F
5 ? /
O.i$e of Silicon+
The o#ide of silicon i.e. silicon dio#ide (!i/=) is the mostimportant compound of silicon. !ilicon dio#ide is also called!ilica. !ilica occurs in nature as !and and uart,. In it eerysilicon atom is attached tetrahedrally to four o#ygen atomsand each o#ygen atom is attached to t"o silicon atoms. Eachsilicon atom is at the centre of tetrahedron "ith o#ygen atoms
lying on the four corners of the tetrahedron. !i/=
differs muchfrom 5/= as the silicon dio#ide e#ists as polymer (!i/=)n "hilecarbon dio#ide e#ists as monomer. %itreous (glass like) silica has follo"ing characters.
(i) 7igh transparency to light.(ii) %ery lo" thermal e#pansion.(iii) E#cellent insulator.(i) 7ard$ brittle and elastic.() Insoluble in "ater and inert to"ards many
reagents.(i) esistant to all acids e#cept 76.(ii) %ery refractory (stubborn) does not soften bello"
? to @o5.
X X X/ / /X X X!i !i !i
/ / / // / /X X X!i !i !i
/ / / /
/ / /X X X
uart, is the most common crystalline form of silicon dio#ide.It has follo"ing characteristics+
(i) It is hard.(ii) It is brittle.(iii) It is refractor.(i) It is colourless.() It is crystalline solid.
Caron can for Multiple Bon$! /hile Silicon Cannot;
The si,e of carbon atom is small. The partially filled &y and&, orbitals of carbon are close to each other. These orbitalscan oerlap side "isely and can form the &i bonds. 2hile!ilicon has bigger si,e as compare to carbon. Its &y and &,
orbitals are far a"ay and cannot oerlap side "isely so theycannot form the multiple bonds.
The aci$-a!e eha(iour of the %roup @ o.i$e!
The o#ides of the elements at the top of Group > are acidic$but acidity of the o#ides falls as you go do"n the Group.To"ards the bottom of the Group$ the o#ides become more
basic - although "ithout eer losing their acidic character completely.
An o#ide "hich can sho" both acidic and basic properties issaid to be amphoteric .
The trend is therefore from acidic o#ides at the top of theGroup to"ards amphoteric ones at the bottom.
Carbon and silicon dioxides
These are both "eakly acidic.
With water
!ilicon dio#ide doesnNt react "ith "ater$ because of thedifficulty of breaking up the giant coalent structure.
5arbon dio#ide does react "ith "ater to a slight e#tent toproduce hydrogen ions (strictly$ hydro#onium ions) andhydrogencarbonate ions.
/erall$ this reaction is+
The solution of carbon dio#ide in "ater is sometimes kno"nas carbonic acid$ but in fact only about .Q of the carbon
dio#ide has actually reacted. The position of euilibrium is"ell to the left-hand side.
With bases
5arbon dio#ide reacts "ith sodium hydro#ide solution in thecold to gie either sodium carbonate or sodiumhydrogencarbonate solution - depending on the reactingproportions.
!ilicon dio#ide also reacts "ith sodium hydro#ide solution$ butonly if it is hot and concentrated. !odium silicate solution isformed.
Uou may also be familiar "ith one of the reactions happeningin the *last 6urnace e#traction of iron - in "hich calcium o#ide(from the limestone "hich is one of the ra" materials) reacts"ith silicon dio#ide to produce a liuid slag$ calcium silicate.This is also an e#ample of the acidic silicon dio#ide reacting"ith a base.
%ernaiu> tin an$ lea$ o.i$e!
he monoxides
All of these o#ides are amphoteric - they sho" both basic andacidic properties.
6or e#ample$ they all react "ith concentrated hydrochloricacid. This can be summarised as+
. . . "here 8 can be Ge and !n$ but unfortunately needsmodifying a bit for lead.
ead(II) chloride is fairly insoluble in "ater and$ instead of getting a solution$ it "ould form an insoluble layer oer thelead(II) o#ide if you "ere to use dilute hydrochloric acid -stopping the reaction from going on.
7o"eer$ in this e#ample "e are talking aboutusing concentrated hydrochloric acid.
The large e#cess of chloride ions in the concentrated acidreact "ith the lead(II) chloride to produce soluble comple#essuch as &b5l>=-. These ionic comple#es are soluble in "ater and so the problem disappears.
'nfortunately$ it means that you hae more to rememberY
The acidic nature of the oxides
All of these o#ides also react "ith bases like sodiumhydro#ide solution. This time "e can generalise "ithoute#ception+
ead(II) o#ide$ for e#ample$ "ould react to gie &b/==- -
plumbate(II) ions.
alogen!
The "ord halogen means salt former. 7alogens belong togroup %II-A. This group consists of the elements "hich aregien in the follo"ing table.
%roup 2-"H6 s=$ =s=$ =p? :7e;=s=$ =p?
5l s=$ =s=$ =p@$ <s=$ <p? :0e;<s=$ <p?
<?*r s=$ =s=$ =p@$ <s=$ <p@$ >s=$
<d$ >p?:Ar;<d$>s=$ >p?
?<I s=$ =s=$ =p@$ <s=$ <p@$ >s=$
<d$ >p@$ ?s=$ >d$ ?p?:4r;>d$?s=$?p?
C? At s=$ =s=$ =p@$ <s=$ <p@$ >s=$
<d$ >p@$ ?s=$ >d$ ?p@$
@s=$ >f >$ ?d$ @p?
:8e;>f >$?d$@s=$@p?
General Properties+
(i) Their general electronic configuration is ns=$ np?.(ii) All halogens are non-metals.(iii) They e#ists as discrete diatomic molecules 6=$ 5l=$ *r =$
I=$ At=.(i) Their melting and boiling points increases do"n the
group. Thus from top to bottom they change from gasto solid. Astatine is radioactie and its half life is
green*romine liuid ?H o5 dark red(apours reddish bro"n)
Iodine solid C> o5 darkcrumbly (apours iolet)
Astatine solid <C o5 black(apours dark)
() 7alogens hae irritating odours and they attack skin.*romine causes burns that heal slo"ly.
(i) They hae seen electrons in their alence shell.(ii) They hae high ioni,ation energies$ electron affinities
and electronegatiities.(iii) They form binary compounds among themseles$
called interhalogens. Their capacity to combine "ith
number of other halogen atoms increases do"n thegroup. This is due to aailability of more orbitals "ithincreasing atomic number. Thus one other halogenatom combines "ith fluorine combine "hile seenother halogen atoms combine "ith iodine.
65l 5l6< *r6? I6
(i#) 5ommon o#idation state for halogens is -$ but theyalso sho" $ <$ ?$ and o#idation states in their
compounds. 7o"eer fluorine does not sho" positieo#idation state as it has highest electronegatiity.(#) 7alogens are good o#idi,ing agent$ ho"eer their
o#idi,ing po"er decreases do"n the group. Their o#idi,ing po"er depends upon (a) dissociation energyand (b) electron affinity (c) reduction potential.
(#i) They form ionic compounds "ith group I-A and groupII-A elements.
(#ii) 7alogens directly reacts "ith hydrogen under differentconditions to produce their hydrides (7ydrogenhalides).
The order of reactiity of halogens to"ards thisreaction is
6= Z 5l= Z *r = Z I=
As the si,e of halogen increases$ the bond energyof 7 F 8 bond decreases and thus stability of halide decreases also polarity of the bonddecreases.The order of stability and polarity is 76 Z 75lZ 7*r Z 7I2hile order of reactiity of halogen acids is 7I
Z 7*r Z75l Z 76
Bon$ enthalpie! 'on$ energie! or on$ !trength!*
*ond enthalpy is the heat needed to break one mole of acoalent bond to produce indiidual atoms$ starting from theoriginal substance in the gas state$ and ending "ith gaseousatoms.
!o for chlorine$ 5l=(g)$ it is the heat energy needed to carryout this change per mole of bond+
6or bromine$ the reaction is still from gaseous bromine
A coalent bond "orks because the bonding pair isattracted to both the nuclei at either side of it. It is thatattraction "hich holds the molecule together. The si,eof the attraction "ill depend$ amongst other things$ onthe distance from the bonding pair to the t"o nuclei.
As "ith all halogens$ the bonding pair "ill feel a netpull of from both ends of the bond - the charge onthe nucleus offset by the inner electrons. That "ill still
be the same "hateer the si,e of the halogen atoms. As the atoms get bigger$ the bonding pair gets further from the nuclei and so you "ould e#pect the strengthof the bond to fall.
he bond enthalpies of the5l-5l$ *r-*r and I-I bondsfall Pust as you "ould
e#pect$ but the 6-6 bond is"ay out of lineY
*ecause fluorine atoms areso small$ you might e#pecta ery strong bond - in fact$it is remarkably "eak.There must be another
factor at "ork as "ell.
As "ell as the bonding pair of electrons bet"een the t"oatoms$ each atom has < non-bonding pairs of electrons inthe outer leel - lone pairs. 2here the bond gets ery short
(as in 6-6)$ the lone pairs on the t"o atoms get close enoughtogether to set up a significant amount of repulsion.
In the case of fluorine$ this repulsion is great enough tocounteract uite a lot of the attraction bet"een the bondingpair and the t"o nuclei. This obiously "eakens the bond.
2here the halogen atom is attached to a hydrogen atom$ thiseffect doesnNthappen. There are nolone pairs on ahydrogen atomY
As the halogen atomgets bigger$ thebonding pair getsmore and moredistant from thenucleus. Theattraction is less$ and
the bond gets "eaker - e#actly "hat is sho"n by the data.There is nothing complicated happening in this case.
This is important in the thermal stability of the hydrogenhalides - ho" easily they are broken up into hydrogen and thehalogen on heating.
7ydrogen fluoride and hydrogen chloride are ery stable toheat. They donNt split up into hydrogen and fluorine or chlorineagain if heated to any normal lab temperature.
7ydrogen bromide splits slightly into hydrogen and bromineon heating$ and hydrogen iodide splits to an een greater e#tent.
As the bonds get "eaker$ they are more easily broken.
2e are going to use the *ronsted-o"ry definition of an acidas a proton donor. 7ydrogen chloride is an acid because itgies protons (hydrogen ions) to other things. 2e are going toconcentrate on its reaction "ith "ater.
7ydrogen chloride gas is ery soluble in "ater$ reacting "ith itto produce hydrochloric acid. The familiar steamy fumes ofhydrogen chloride in moist air are caused by the hydrogenchloride reacting "ith "ater apour in the air to produce a fog
of concentrated hydrochloric acid. A proton is donated from the hydrogen chloride to one of thelone pairs on a "ater molecule.
A co-ordinate (datie coalent) bond is formed bet"een theo#ygen and the transferred hydrogen ion.
Theeuation for the reaction is+
The 7</ ion is the hydro#onium ion (also kno"n as thehydronium ion or the o#onium ion). This is the ion that "e areactually talking about "hen "e "rite 7
(a).
2hen hydrogen chloride dissoles in "ater (to producehydrochloric acid)$ almost Q of the hydrogen chloride
molecules react in this "ay. 7ydrochloric acid is therefore astrong acid . A strong acid is one "hich is fully ionised insolution.
7ydrogen bromide and hydrogen iodide dissole in (and react"ith) "ater in e#actly the same "ay as hydrogen chloridedoes. 7ydrogen bromide reacts to gie hydrobromic acid3hydrogen iodide gies hydriodic acid. *oth of these are alsostrong acids.
)$rofluoric aci$ a! an e.ception
*y contrast$ although hydrogen fluoride dissoles freely in"ater$ hydrofluoric acid is only a "eak acid - similar instrength to organic acids like methanoic acid. The reason for this is uite complicated.
ali$e on! a! #e$ucing "gent!
The bromide ions are strong enough reducing agents toreduce the concentrated sulphuric acid. In the process thebromide ions are o#idised to bromine.
The bromide ions reduce the sulphuric acid to sulphur dio#ide
gas. This is a decrease of o#idation state of the sulphur from@ in the sulphuric acid to > in the sulphur dio#ide.
Uou can combine these t"o half-euations to gie the oerallionic euation for the reaction+
2hat you see in this reaction are the steamy fumes of hydrogen bromide contaminated "ith the bro"n colour of
The elements of Dd or Df block "hich form one or more stableions "ith partially filled d or f orbitals are called transitionelements. As they hae properties bet"een s-block and p-block so they are called transition elements. They are diidedinto t"o categories+
a) &ain transition elements or outer transition metals: d-block elements are called main or outer transitionelements.
• They hae partially filled (n-) d orbitals in groundstate.
• They are further diided intost transition series or <d series "hich consist of
=!c to =H5u=nd transition series or >d series "hich consist of
<HU to > Ag<rd transition series or ?d series "hich consist of
?a to H Au>th transition series or @d series "hich consist of
CH Ac to HMt (Metnerium)
b) Inner transition elements or metals: f-blockelements are called inner transition elements.
• They hae partially filled (n-=) f orbitals in ground state• They consist of t"o hori,ontal ro"s at the bottom of
periodic table.
0i!tingui!hing Propertie! of Tran!ition Metal!+
. They are hard metals and hae high meltingand boiling points.=. They are good conductor of heat and
<. They sho" ariable o#idation states andalencies.
>. Their compounds are mostly coloured in solidstate as "ell as in aueous state.
?. !ome of these form paramagnetic compounds.@. They form comple#es or coordination
compounds.. They form alloys.C. These elements and some of their compounds
act as solid catalysts.General Characteristics+
. "toic an$ onic #a$ii+The atomic radii across period$ decrease rapidly atthe start then remains almost same and then forlast elements it increases. This increase
is probably due to the filled < d orbitals gie moreshielding to outer shell so atomic radii increases.
5hanges in ionic radii across period are irregular.
[!c \ [Ti [9n
adii [%[5u [5r [Mn [6e [5o
[0i
Atomic 0umber J
. Melting an$ Boiling Point!+
Melting and boiling points of transition metals are ery high due to strong
binding forces among their atoms. M.& 1 *.&increase in a series up to middle of the series andthen decreases up to end of the series. This is due
to the reason that up to middle of series number of unpaired electrons increase so binding forcesincreases thus M& 1 *& increase$ the unpaired delectrons also participate in binding. Then on"ardpairing of electrons take place so binding forcesdecrease thus M& 1 *& decrease.
[% [5r [Ti 6e 5o 0i
\ [!c [ [ [M.& [ Mn [5u [5a [9n
[4
Period!<) Atomic 0umber J
. oni+ation Energ)+Their ioni,ation energies are intermediate of s-block and p-block. Thus they are capable offorming both ionic as "ell as coalent compounds.
=. O.i$ation !tate!+
They sho" ariable o#idation states and this isdue to the reason that beside outer s-electrons d-electrons also participate in bonding. In series upto middle$ number of o#idation states increasesand then decreases as can be seen in <-d series.
igands "hich donate more than t"o lone pairs of electrons to form coordinate coalent bond "ith centraltransition metal are called polydentate ligands.e.g. Ethylene diamine tetra acetic acid (EBTA) ion
-
//5 57= 57= 5//-
0 57= 57= 0-//5 57= 57= 5// -
It is a he#adentate ligand
(%) Coordination umber :0umber of monodentate ligands attached to centraltransition metal or number of coordinate coalent bonds thatare made by transition metal$ is called coordination number.4no"n coordination numbers are =$<$>$?$@$$C and H.e.g. (i) In 4>:6e(50)@;$ coordination number of 6e is @.e.g. (ii) In :0i(5/)>;$ coordination number of 0i is >.
5omple#es "ith > and @ coordination number are ery
common "hile comple#es "ith coordination number ? areless common.
Ag usually sho"s coordination number =0i$ 5u$ &t usually sho" coordination number >6e$ 5o usually sho" coordination number @
(d) Coordination Sphere:
The central metal atom along "ith ligands is calledcoordination sphere. It is placed in suare brackets. It may beanionic$ cationic or neutral e.g. 4>:6e(50)@;$ :5u(07<)>;!/>
and :0i(5/)>; are anionic$ cationic and neutral respectiely.
<d >s >pBue to strong interaction "ith ligands the unpaired d electronsare paired up and as a result t"o orbitals of d sub-shellbecome acant. T"o acant d-orbital$ one acant s-orbital
and three acant p-orbital hybridi,e and gie si# acant d=
igands donate their lone pairs of electrons to the acanthybrid orbitals and thus form coordinate coalent bonds "ithcentral transition metal and as a result comple# is formed.
Noenclature+I'&A5 names of coordination compounds follo" follo"ingseuence5ation F ligand F transition metal F anion
(i) 0ame of cation is "ritten first if any.(ii) Then name of ligand is "ritten. &refi#es di$ tri$tetra$ penta are used "ith the name ofmonodentate ligand and prefi#es bis$ tris$tetrakis etc are used "ith the name ofbidentate or polydentate ligands to sho" thenumber of ligands. If ligand is anion suffi# D/and for cationic ligand suffi# Dium is used "ith
its name$ "hile no suffi# for neutral ligand Pustits atin name is "ritten.If more than one kind of ligands are there thenfirst the negatie$ then the neutral and at theend the positie ligands are "ritten. If morethan one kind of Fe ligands are there then
alphabetical order is follo"ed amongthemseles$ !ame practice "ill be follo"ed fore and neutral ligands if they are of morethan one kind.&refi# ^ is used "ith the names of bridgingligands and they are "ritten after normalligands.
nionic ligands:
50-
5yano !50-
Thiocyanato 0/=-
0itro
5l- 5hloro !/>-= !ulphato
!=/<-=
Thiosulphato 5=/>-=
/#alato /7-
7ydro#o 5/<-=
5arbonato 07=- Amido
eutral ligands:07< Ammine 7=/ Aua 5/
5abonyl 0/ 0itrosyl 77=0 F 57= F 57= F 07= Ethylene diamine (en)
Cationic ligands:
7ydra,inium 0=7? (:07=`
07<)$
0itrosonium 0/$ &yra,inium
(iii) 0o" name of transition metal is"ritten. If coordination sphere isanion then 0 suffi# Date is used "ith theatin name of transition metal$ other"ise PustA English name is "ritten.
(i) 6ollo"ing the name of transition metal$o#idation state of the metal is "ritten in omannumeral in parenthesis.
() Anion is "ritten at the end if any.!ome e#amples+4>:6e(50)@; &otassium he#acyano ferrate(II):5o(07<)>5l=;5l Bichloro tetraammine 5obalt
If you add hydro#ide ions$ these react "ith thehydrogen ions. The euilibrium tips to the left toreplace them.
Ma6ing pota!!iu $ichroate'2* cr)!tal!
!tarting from a source of chromium(III) ions such aschromium(III) chloride solution+ Add potassium hydro#ide solution to gie first a grey-green precipitate and then the dark green solutioncontaining :5r(/7)@;<-ions. This is all described indetail further up the page. 0otice that you hae touse potassiu" hydro#ide. If you used sodiumhydro#ide$ you "ould end up eentually
"ith sodiu" dichromate(%I).&otassium dichromate "ill react "ith any e#cesshydrogen pero#ide to gie initially an unstable deepblue solution and it eentually gies the originalchromium(III) ions again.This is done by boiling the solution. 7ydrogenpero#ide decomposes on heating to gie "ater ando#ygen. The solution is boiled until no more bubbles of o#ygen are produced. The solution is heated further toconcentrate it$ and then concentrated ethanoic acid isadded to acidify it. /range crystals of potassiumdichromate are formed on cooling.
The o#ygen "ritten in suare brackets Pust means Ro#ygenfrom an o#idising agentR.
Mangane!e
It is a chemical element$ designated by the symbol Mn. It hasthe atomic number =?. It is not found as a free element innature3 it is often found in combination "ith iron$ and inmany minerals. Manganese is a metal "ith important
Alkaline potassium manganate(%II) solution o#idises anyhydrocarbon side chain attached to a ben,ene ring back to asingle -5//7 group. &rolonged heating is necessary.
6or e#ample+ In the caseof the ethyl side chain$you "ill also get carbon
dio#ide. 2ith longer sidechains$ you "ill get allsorts of mi#tures of other products - but in eachcase$ the main product"ill be ben,oic acid.
!ing pota!!iu anganate'2* a! an o.i$i!ing agent intitration!
&otassium manganate(%II) solution is used to find theconcentration of all sorts of reducing agents. It is al"ays usedin acidic solution.
6or e#ample$ it o#idises
• iron(II) ions to iron(III) ions
• hydrogen pero#ide solution to o#ygen
• ethanedioic acid to carbon dio#ide (This reaction hasto be done hot.)
• sulphite ions (sulphate(I%) ions) to sulphate ions(sulphate(%I) ions)
In each case$ the half-euation for the manganate(%II) ions inacidic solution is+
+oing the titration
The potassium manganate(%II) solution al"ays goes into the
burette$ and the other solution in the flask is acidified "ithdilute sulphuric acid.
As the potassium manganate(%II) solution is run into the flaskit becomes colourless. The end point is the first faint trace ofpermanent pink in the solution sho"ing that there is a tinye#cess of manganate(%II) ions present.
ron+
It is an important and useful metal. It "as kno"n toancient Egyptians since > *5. *ut its e#traction startedsince = *5. In India its e#traction started since @ *5. Itbelongs to group %III-* of periodic table.
Occurrence+ After Aluminum it is most abundant metal on the earth
crust. It is found in the form of meteor$ rocks$ mineral$ soils$plants and animals etc. *roken piece of rock that comes fromstars and burn in earthSs atmosphere is called meteor.
@. 5opper &yrite (6oolSs Gold) 5u6e!=.Coercial for! of ron+
Iron is aailable commercially in follo"ing three forms.They differ in their carbon contents.
. &ig iron or 5ast iron. It contains =.? F >.? Qcarbon.
=. 2rought iron. It contains .= F .=? Q carbon.
<. !teel. It contains . F .? Q carbon.>.
ron an$ it! ion! a! catal)!t!
ron a! catal)!t in the aer Proce!!
The 7aber &rocess combines nitrogen and hydrogen intoammonia. The nitrogen comes from the air and the hydrogenis obtained mainly from natural gas (methane). Iron is used asa catalyst.
ron ion! a! a catal)!t in the reaction et/eenper!ulphate ion! an$ io$i$e ion!
The reaction bet"een persulphate ions (pero#odisulphateions)$ !=/C
=-$ and iodide ions in solution can be catalysedusing either iron(II) or iron(III) ions.
There is an important difference here bet"een the behaiour of iron(II) and iron(III) ions.
Iron(II) ions and carbonateions
Uou simply get a precipitate of
"hat you can think of as iron(II)carbonate.
Iron(III) ions and carbonate ions
The
he#aauairon(III) ion is sufficiently acidic to react "ith the"eakly basic carbonate ion.
If you add sodium carbonate solution to a solution of he#aauairon(III) ions$ you get e#actly the same precipitateas if you added sodium hydro#ide solution or ammoniasolution.
This time$ it is the carbonate ions "hich remoe hydrogenions from the he#aaua ion and produce the neutral comple#.
Bepending on the proportions of carbonate ions tohe#aaua ions$ you "ill get either hydrogencarbonate ions
*ranch of chemistry "hich deals "ith the scientificstudy of structure$ properties$ composition$ reaction andpreparation of compounds containing carbon like7ydrocarbons and their deriaties are called organic
chemistry.7ydrocarbons are those compounds "hich e#clusiely
containing carbon and 7ydrogen in their structure.
According to %ital 6orce TheoryS organic compounds "erebelieed to be the compounds prepared by liing organisms.
*ut later on $ in C=C$ 6riedrick 2holer ( a Germanchemist)$ prepared 'rea (an organic compound) in laboratoryby heating Ammonoium cyanate. It proed the ital forcetheory to be "rong.
/
07>50/ 7=0 F 5 F 07=
('rea)
0o"-a-days organic compounds are defined as compoundsof carbon "ith fe" e#ceptions. These e#ceptions are 5/$
5/=$ 5!=$ 5arbonates (5/<-=
)$ *icarbonates (75/<-)$
5yanides (50-)$ 5yanates (50/-)$ 5arbides 5
->) etc.
Source! of Organic Copoun$!:
The maPor sources of organic compounds are &lants$ 5oal$&etroleum and 0atural Gas.
by the decay of liing organisms burried in the earthcrust. &etroleum in unrefined form is called crude oil. Ithas un- pleasant$ irritating smell due to presence of sulpher contents.&etroleum reseres are found in !anghar and *adinof !ind$ Bera Gha,i 4han district of &unPab proince$and 4arak area of 4&4 proince.
i%# Natural &as$
It is found in porous rocks and it is blend of hydrocarbons. Mostly it "as fond "here petroleumoccurs. It contains Methane$ Ethane$ &ropane andbutane. &reiously it "as belieed that natural gas"as found only at marshy places so it is also kno"nas marsh gas. In &akistan it "as first discoered at!'I (*aluchistan). The only difference bet"eennatural gas and petroleum is the no of hydrocarbons
( 5- 5>). In 0atural gas it is lo" chain hydrocarbons"hile in petroleum the hydrocarbon is of larger chain(5?- 5>)
It is the chemical process inolingthe decomposition of feedstock by heating to a hightemperature3 the term generally applies to processingof organic material in the absence of air or in the presence oflimited amounts of o#ygen or other reagents$ catalysts$or solents$ such as steam or phenols. It is an applicationof pyrolysis. The process breaks up or NcracksN largemolecules. 5oke$ coal gas$ gas carbon$ coal tar$ *uck-
minister-fullerene$ ammonia liuor$ and Rcoal oilR historically$are e#amples of commercial products of the destructiedistillation of coal.
Coal Tar:
It is mi#ture of more than = organic compounds$ "hich canbe separated by fractional distillation. It is a bro"n or black
liuid of e#tremely high iscosity. 5oal tar is among the by-products "hen coal is carboni,ed to make coke or gasified tomake coal gas. 5oal tars are comple# and ariable mi#turesof phenols$ polycyclic aromatic hydrocarbons (&A7s)$and heterocyclic compounds.
Coal %a!:
It is mi#ture of carbon mono o#ide and 7ydrogen also calledas "ater gas and to"n gas. It is a flammable gaseous
fuel made from coal and supplied to the user ia a pipeddistribution system. To"n gas is a more general term referringto manufactured gaseous fuels produced for sale toconsumers and municipalities.
"onical Liuor:
It isa concentrated solution of ammonia$ ammonium compounds$and
ii. 2oolen products$ rubber$ plastics$ cosmetics$paints$ medicines$ shoe polish$ and many other
daily use items are mainly organic in nature.
Characteri!tic! of Organic Copoun$!:/rganic compounds hae follo"ing common
characteristics. They must contain 5arbon.=. They hae lo" melting and boiling points.<. They decompose at lo" temperature.>. They are mostly flammable.?. They are coalent compounds.@. Their reactions are usually slo".. They mostly sho" isomerism.
e.g. 5/= is not organic compound as it has some of theaboe mentioned characteristics but not all on the other handsucrose (5=7==/) is an organic compound as it possessesall of the aboe mentioned characteristics. #ea!on! for (er) large nuer of organic copoun$!:
Bue to follo"ing reasons number of organic
compounds is ery large.. Tetra alency of 5arbon+ As carbon has tetra alency so it
can gie arious combinations "ith other atoms e.g.carbon gies ? combinations "ith 7 and 5l i.e. 57>$57<5l$ 57=5l=$ 575l<$ 55l>.
=. 5atenation+ !elf linkage of atoms of an element is called
catenation$ this ability is ma#imum in carbon. Bue to thisreason carbon can form long chains$ branched chains andrings.
<. Isomerism+ /rganic compounds hae arious isomerse.g (i) &entane 5?7= sho"s < isomers i.e. n-pentane$iso pentane$ neo pentane etc.e.g (ii) molecular formula
5=7@/ represents t"o isomers 57<-/-57< 1 5=7?/7.>. Multiple *onds+ 5arbon is capable of forming multiplebonds among its o"n atoms as "ell as "ith other atomse.g. 57<-57<$ 57=K57=$ 5757 etc.
Buc6) Ball!:
*uck minster fullerene (or bucky-ball) is a
spherical fullerene molecule "ith theformula 5@. It has a cage-like fused-ringstructure (truncated icosahedron) "hich
resembles a soccer ball$ made of t"enty he#agons andt"ele pentagons$ "ith a carbon atom at each erte# of eachpolygon and a bond along each polygon edge.
It "as first generated in HC? by 7arold 4roto$ Lames .7eath$ !ean /N*rien$ obert 5url$ and ichard
!malley at ice 'niersity. 4roto$ 5url and !malley "erea"arded the HH@ 0obel &ri,e in 5hemistry for their roles inthe discoery of buckminsterfullerene and the related class of
molecules$ the fullerenes. The name is a referenceto *uckminster 6uller $ as 5@ resembles histrademark geodesic domes. *uckminsterfullerene is the most
common naturally occurring fullerene molecule$ as it can be
The carbon attached to one other carbon or no other carbon is called primary carbon$ "hile hydrogens attached toprimary carbon are called primary hydrogens e.g in follo"ingcompound 5arbon 0o.$? and that of methyl group areprimary carbons and their hydrogens are primary hydrogens.
<-Methyl pentane
The carbon attached to t"o other carbons is calledsecondary carbon$ "hile hydrogens attached to secondary
carbon are called secondary hydrogens e.g in aboementioned compound 5arbon 0o.=$> are secondary carbonsand their hydrogens are secondary hydrogens. The carbonattached to three other carbons is called tertiary carbon$ "hilehydrogen attached to tertiary carbon is called tertiaryhydrogen e.g in aboe mentioned compound 5arbon 0o.< istertiary carbon and its hydrogen is tertiary hydrogen.
"l6)l %roup:
A group obtained after the loss remoal of hydrogen atomthe an alkane is called an alkyl group. It is represented by D. means remainders$ as alkyl group is al"ays attached "ithany functional group.
Obser%ation and inference+If "ater drops appeared on cooler parts of the testtube or anhydrous copper sulphate turned blue thenhydrogen is present in the compound.
* 0etection of O.)gen:-
/#ygen cannot be detected by any direct method but
for its detection some indirect methods are used.
. The gien organic compound is heated alone in a drytest tube usually in 0itrogen atmosphere. 6ormation of "ater droplets on the cooler part of test tube clearlyindicates the presence of o#ygen.
=. Bifferent tests are applied for the detection of o#ygencontaining functional group like$ alcohol$ aldehyde$
ketone and carbo#ylic acid. If any functional group isdetected$ it sho"s the presence of o#ygen.
<. The most important test for the presence of o#ygen iscombustion analysis$ in "hich percentage of carbonand hydrogen are determined. Then sum of carbon
and hydrogen percentage is subtracted from . Theremaining percentage "ill be o#ygen.Q /#ygen K F ( Q 5arbon Q 7ydrogen).
Cou!tion "nal)!i!:
It is one of the estimation techniues. A "eighedamount of sample is placed in combustion tube. The tube isconnected to cylinder of o#ygen gas and the gas is passed for some time to remoe air from the combustion tube.
5/=$ 7=/$ /= 5/=$ /=
J J/= JJ unreacted/= !ample boat
Mg(5l/>)= ?Q 4/7 Magnesium per chlorate a &otassium hydro#ide
(2ater absorber) (5/= absorber)The t"o u-shaped tubes$ one containing "ater
absorber and other containing 5/= absorber are "eighed andconnected to the combustion tube as sho"n in fig. Thecompound in the combustion tube is strongly heated to
burning. 5arbon and hydrogen (if any) of the compound "illbe conerted to 5/= and 7=/ respectiely. The increase inthe "eight of absorbers "ill gie the mass of 5/= and 7=/produced. 6rom the mass of 5/= percentage of 5arbon iscalculated "hile from the mass of 7=/ percentage of 7ydrogen is calculated.
6erric thiocyanide (reddish colour)Note:(i) !ometimes "hen amount of nitrogen present is small$
the &russian blue ferri ferro cyanide is present incolloidal form and the solution looks green.
(ii) 2hen the alkaline solution is acidified "ith 75l$ theyello" colour of 6e5l< makes the blue colour toappear green.
(iii) i and 4 cannot be used in place of 0a because ireacts slo"ly "here as 4 reacts igorously and cannotbe handled properly. Moreoer lithium compounds arecoalent.
The presence of nitrogen in an organic co"pound can alsobe detected by the following "ethods+
2hen a small amount of the organic compound isburnt smell of burning feathers indicates the presenceof nitrogen ho"eer ignition test is not a sure test.
(=) So$a Lie Te!t: The gien organic compound ( parts) is heated "ithsoda lime (= &arts). Eoling of ammonia indicates thepresence of nitrogen.
Liitation:Many classes of nitrogen compounds like nitro anddia,o deriaties do not respond to this test.
(*) 0etection of !ulphur:
To detect sulphur t"o tests could be performed.
Te!t-1
(i)Take a fe" mls of assaigneSs solution in a test tube.(ii) Add acetic acid solution.
(ii) Then add lead acetate solution.
Obser%ation and inference+
Appearance of black precipitate of lead sulphideindicates presence of sulphur in the compound.
6riedrich 4. *eilstein-a ussian chemist introduce thistest. A copper "ire is cleaned and flattened at one end isheated in a *unsen burner flame till it ceases to impart anygreen or blue colour to the flame. It is touched "ith theorganic compound and reheated in the flame. A olatile$
copper halide is formed "hich imparts green or blue colour tothe flame. It indicates the presence of a halogen in theorganic compound.
imitations+(i) 5ompounds like pyridine$ urea and thiourea
"hich do not contain halogens also respond tothis test.
(ii) It does not tell about the particular halogenpresent in the organic compound.
Noenclature+
There are t"o systems of naming organic compounds.
(i) 5ommon system or Triial 0ames+
In this system names are deried from source or their property or their structure etc.e.g 'rea from urine (source)$ 5itric acid from citrusplant (source).
• If the locant or sum of locants of the functional group is
same for both ends then numbering is carried out fromthat end "hich gies smallest locant or sum of locants tothe substituents. *ut first point of difference must getsmaller locant.
• 0e#t preference is gien to more electronegatie groupand last preference is gien to larger alkyl group.
!tep-III 0aming+
• !ubstituents are named before parent name and namesof substituents are preceded by their locants. At endparent name is "ritten and it is preceded by its locant(s).
• If same substituent is occurring more than one time thenprefi#es di$ tri$ tetra$ penta etc are used "ith its name andlocant of each is "ritten each time.
• If substituents of more than one kind are there then their names are "ritten in alphabetical order.
• T"o numbers are separated by comma bet"een them$ anumber and a name are separated by a hyphen bet"eenthem "hile t"o names are separated by a space bet"eenthem.
Those hydrocarbons in "hich all the carbon atoms haesingle coallent bond "ith hydrogen or "ith other atoms arecalled saturated hydrocarbons. 5arbon atom alency is fullysatisfied. 7ere each carbon is bonded to four other atoms.These are also kno"n as alkanes$ "hich may be branchedchain or straight chain molecules.
BD n-!aturate$ )$rocaron!:
7ydrocarbons "hich contains at-least one double or triplebond in their structural formula are called un-saturatedhydrocarbons.'nsaturated hydrocarbon "here carbon and carbon atomcontain at least one double bond are called alkenes$ haing
general formula of 5n7=n. "hile those haing at least onetriple bond bet"een carbon and carbon atoms are calledalkynes haing general formula of 5n7=n-=. *oth alkenes andalkynes may be branched or straight chain molecules.
C)cloal6ane!:7ydrocarbons haing fused ring or closed ring of carbon atoms arecalled cyclic hydrocarbons$ cyclo
alkanes. They hae t"o hydrogenatoms less than open chain alkanes.E#amples are cyclobutane$ cyclohe#ane etc.
"roatic )$rocaron!Those hydrocarbons "hich contain at-least one ben,ene ringin their structure are called aromatic hydrocarbons. The term
aromatic "as first introduced by 4ekule$ "ho "anted toclassify ben,ene and its deriaties.
Characteri!tic! of "roatic )$rocaron!:
• These are cyclic compounds "hich contains conPugatedouble bonding system like in ben,ene.
• They resist to undergo addition type of reactions.• They faor the electrophilic substitution reactions.• They neer faor the elimination reactions.
Alkanes are open chain saturated hydrocarbonshaing general formula 5n7=n=. They are less reactie andhence are also called &araffins.
%eneral Metho$! of Preparation of "l6ane!+
) *y 7ydrogenation of unsaturated hydrocarbons (!abatier !endernSs reaction)+ Alkanes can be prepared by passing alkenes or alkynes
oer finely diided nickel or platinum or palladium catalyst.The catalyst changes molecular hydrogen to atomic hydrogen"hich can break pi-bonds of alkenes or alkynes and "ill beadded to them. Addition of hydrogen to alkenes or alkynes iscalled hydrogenation and is also called !abatier-!endernSs
eaction or !-! eaction.2hile using 0ickel$ heating is reuired from =?-<
o5
but in case of &latinum and palladium no heating is reuired.
=) *y eduction of Alkyl 7alides+Molecular hydrogen can not reduce alkyl halides$
ho"eer atomic hydrogen can reduce alkyl halides and giesalkanes. Therefore alkyl halides are treated "ith 9inc inpresence of dil 75l$ nascent hydrogen is produced "hichreduces alkyl halides to corresponding alkanes.
<) *y 7ydrolysis of Grignard eagent+ Alkyl Magnesium 7alides ( Mg 8) are called
Grignard reagents. These are organo-metalliccompounds.7ydrolysis of grignard reagents producecorresponding alkanes.
>) *y 2urt,Ss eaction+2urt, discoered this method in CC?. The reaction of alkylhalides "ith sodium metal in presence of anhydrous ether
produces alkanes and is called 2urt,Ss reaction.In this method higher alkanes are produced.
%eneral Ph)!ical Propertie! of "l6ane!+. At room temperature and pressure st four alkanes
(i.e. from 5 to 5>) are colourless and odourlessgases. Alkanes from 5? to 5 are colourless andodourless liuids "hile alkanes from 5C and on"ardare colourless and odourless solids.
=. The melting and boiling points of alkanes are lo"er
than alcohols of comparable molecular masses.<. The melting and boiling points of alkanes sho"gradual increase "ith increasing molecular masses.7o"eer the higher alkanes sho" no marked changein melting and boiling point.
>. More is the number of branches in alkanes lo"er "illbe the boiling points.
?. Alkanes are non-polar so are soluble in non-polar
solents like ether$ acetone$ ben,ene$ carbon tetrachloride etc.@. !pecific graity$ iscosity of alkanes increases "ith
increasing molecular masses.
Structure of "l6ane!
The hybridi,ation in "hich one s-orbital and three p-orbitals
are mi#ed to form four identical hybrid orbitals is called sp<
hybridi,ation. The four sp< hybrid orbitals are degenerated(hae eual energy) and they are directed in space to four
corners of tetrahedron haing an angle of H.?o
. Each sp<
hybrid orbital has =?Q s-character and ?Q p-character.
7o"eer at eleated temperatures they react "ith thesereagents.
Alkanes being saturated compounds mostly sho" substitutionreactions. Their o#idation is ery difficult thus een strongo#idi,ing agents like 4Mn/>$ 4=5r =/ etc can not o#idi,ethem.
. Halogenation+
7alogens replace hydrogen from alkanes and it iscalled halogenation of alkanes. The order of reactiityof haogens "ith alkanes is
6=Z5l=Z*r =ZI=6luorine sho"s reaction "ith e#plosie iolence.eaction of iodine is slo" and reersible.7alogenation is a substitution reaction and it proceedsthrough free radical mechanism.
a) In dark no reaction occurs
Mechani!: It is a free radical substitution reaction. Its steps are
The reactiity order of aliphatic hydrocarbons is Alkenes Z Alkynes Z AlkanesIt means that alkenes are most reactie in this series.
They hae a double bond "hich consists of a strong sigma() bond (bond energy K C< 4calmol) and a "eak pi ( )-bond (bond energy K @< 4calmol). The density of -electronsis high aboe and belo" the bond a#is. In other "ords -
electrons are a"ay from the nuclei of the carbon atoms sohold of nuclei is less on them. Thus they are e#posed toelectrophilic attack. Thus an electrophile can easily attack andcan break bond by using less energy and therefore alkenesare more reactie.
Alkenes being unsaturated compounds mostly sho"saddition reactions. *eside addition reactions they also sho"o#idation reactions. An o#idi,ing agent can remoe their
loosely bound -electrons.The reactions of alkenes can be diided into threecategories.
"D ddition ,eactions+ Alkenes being unsaturated compounds mostly sho"
addition reactions and the addition is electrophilic addition.
Mechanism+
A polar or temporarily polari,ed molecule approachesto alkene and e end of the molecule pulls its -electrons asa result reagent molecule breaks up and its e ion(electrophile) forms a temporary bond "ith t"o multiplebonded carbons.
T"o products are possible. *utactually only =-haloalkane "ill be obtained asmaPor product. This sho"s that "hen alkene isunsymmetrical then addition take place according
to Marko"nikoffSs rule. 2hich statesD2hen an asymmetric molecule is added to anasymmetric alkene or alkyne then the negatiepart of the molecule to be added goes to thatmultiple bonded carbon "hich has less number of hydrogens and ice ersa.
In aboe mentioned later case addition took place
according to Marko"nikoffSs rule. In case-I primarycarbonium ion "ill be formed "hile in later casesecondary carbonium ion "ill be formed. Thestability of carbonium ions is
Ter-carbonium ion Z !ec-carbonium ion Z &ri-carbonium ion
As in case-II stable carbonium ion is formed soaddition takes place according to Marko"nikoffSs rule.
2hen halogen acid molecule approaches to alkene itse end pulls -electrons and as a result halogen acidmolecule breaks up and e hydrogen ion (acts aselectrophile) forms a temporary bond "ith t"o multiplebonded carbons.
The elecrophile (7ydrogen) makes permanent bond "ith oneof the carbon and leaing e charge on other carbon.
>.
-ddition of Hypohalous -cid +2hen alkenes are treated "ith aueous solution of
hypohalous acids 7/8 addition reaction takeplace to gie halohydrins (haloalcohols).The order of reactiity of halogen acids to"ards this
reaction is7/6 Z 7/5l Z 7/*r Z 7/I
7ypofluorous acid 7ypoclorous acid7ypobromous acid 7ypoiodous acid7ypoiodous acid is nonreactie in this reaction and
?. -ddition of Sulphuric -cid +2hen alkenes are treated "ith cold concentrated
7=!/> addition of acid take place.
In asymmetricalkenes addition takes place according toMarko"nikoffSs rule.
The alkyl hydrogen sulphates on dilution "ith"ater and boiling gie alcohols
Alkyl hydrogen sulphate Alcohol
As acid is replaced by "ater so actually addition of "ater has taken place$ therefore$ the reaction iscalled Hydration of alkenes.
@. Reaction with dilute Sulphuric acid +2hen ethene is treated "ith dilute (Q) 7=!/> inpresence of mercuric sulphate hydration occurs.
BD /xidation ,eactions+
The -bond in alkenes is a "eak bond and .-electrons are loosely bound to carbon nuclei hence aresusceptible for the attack of o#idi,ing agents. Therefore
o#idi,ing agents can easily o#idi,e alkenes. !ome o#idationreactions of alkenes are follo"ing.
. Co"bustion+ Alkenes on burning produce 5/= and 7=/ apoursalong "ith liberation of heat.This is o#idation reaction.
=. Ozonolysis+/,one is highly reactie so it reacts igorously"ith alkenes and produce corresponding alkyleneo,onide. This is o#idation reaction. Alkyleneo,onide then on reaction "ith 9inc dust inpresence of "ater reduces to some aldehyde or ketone or mi#ture of the t"o.
As "ater is recoered so it is acting as catalyst.
<. /poxide 0or"ation+
2hen a mi#ture of alkene and air is passed oer heated siler o#ide catalyst$ an atom of o#ygen adds toalkene molecule and alkylene epo#ide is formed. This is
>. Hydroxylation+2hen alkenes are treated "ith dilute alkaline4Mn/> solution hydro#ylation of alkenes occursand as a result icinal glycols (%icinal dihydro#y
alcohols) are produced. This is also an o#idationreaction. This reaction could be used asidentification for presence of carbon-carbonmultiple bonds and is kno"n as
,aeyer+s test . Becolouri,ation of pink colour of 4Mn/> indicates the presence of carbon-carbondouble or triple bond.
CD Pol)eri+ation+2hen ethene is subPect to a pressure of atmit liuefies. Then on heating liuid ethane to atemperature of -<o5 it polymeri,es to
polyettylene or polythene. If catalysts likealuminium triethyl Al(5=7?)< or titaniumtetrachloride Ti5l> are used a good ualitypolythene is obtained.
!e! of Ethene+Ethene is an important member of alkene family and it
has many uses.
. /n burning mi#ed "ith o#ygen gies o#yethyleneflame "hich is used for "elding and cutting metals=. 6or artificial ripening of green fruits.<. 6or making mustard gas "hich is used in chemical
"eapons. It "as used in first "orld "ar.
Actually it is not gas but liuid that disperse as mist in air.It has mustard like odour. It is a po"erful esicant i.e. causesblisters.
>. It is used as general anaesthetic.?. 6or manufacturing polythene$ a plastic used for bags$bo#es$ cables$ toys etc.
@. 6or making glycol used as antifree,e.. 6or making ethylene dichloride used as solent.C. 6or making ethylene o#ide used as fumigant.H. 6or making ethyl alcohol.
!oeri!:
It is a Greek "ord$ IsoS means same and merS meansmolecular unit.
DThe phenomenon of e#istence of different compounds "ithsame molecular formula but different structural formulae iscalled isomerism and the compounds are called isomers.
Isomers differ in physical or chemical or in both properties.
Chiral Center A structural feature "ithin a molecule that is responsible for itschirality is called chiral center of molecule. A carbon atom"hich is bonded to four different groups is called chiral carbonor asymmetric carbon atom. 6or e#ample lactic acid here
carbon is chiral "hich is attached to four different groups likeleft side methyl$ upper hydrogen$ lo"er hydro#yl and rightcarbo#ylic group.
Optical !oeri!
Those organic compounds "hich hae the same structuralformula but they can rotate the plan of plane polari,ed light to
any direction are called optical isomers. 2hile the actiity torotate the plan of polari,ed light in opposite direction bycompound is called optical actiity. If the light is rotate to rightor clock"ise it is called de#tro rotatry denoted "ith positie
DThe phenomenon of e#istence of differentcompounds "ith same molecular formula but differentpositions of the functional groups is called position isomerismand the compounds are called position isomers.
(iii)6unctional Group Isomerism+
DThe phenomenon of e#istence of differentcompounds "ith same molecular formula but different
functional groups is called functional group isomerism and thecompounds are called functional group isomers.
e.g (ii)Glucose and 6ructose
(i) Metamerism+
DThe phenomenon of e#istence of differentcompounds "ith same molecular formula but haing uneualnumber of carbons on t"o side of functional group is calledmetamerism and the compounds are called metamers.
It is special type of isomerism "hich is functionalgroup isomerism$ in "hich the isomers are in dynamiceuilibrium "ith each other.
B* %eoetric !oeri! 'Ci!-tran! i!oeri!*:
DThe phenomenon of e#istence of different
compounds "ith same molecular and structural formula butdiffer only in position of identical groups in space is calledgeometric isomerism or cis-trans isomerism and thecompounds are called geometric isomers or cis-transisomers.
5arbon atoms Poined by single bond are capable of freerotation about the bond. *ut carbon atoms Poined by double
bond are not capable of free rotation about double bond as itneed first to break pi-bond "hich reuires energy comparableto that "hich needs in chemical reactions. This lack of rotation about double bond gies rise to geometric isomerism.
Alkynes are open chain unsaturated hydrocarbonshaing general formula 5n7= n - =. They hae at least onecarbon-carbon triple bond. 6irst member of this family isacetylene$ the other members of the family are considered asderiaties of acetylene and are hence called acetylenes.
%eneral Metho$! of Preparation of "l6)ne!+
. ,y dehydrohalogenation of %icinal dihaloal.anes+emoal of hydrogen and halogen is calleddehydrohalogenation. 2hen icinal dihalides areheated "ith alcoholic solution of 4/7$ hydrogenand halogen atoms are remoed from adPacentcarbons and in t"o steps alkynes are produced.
=.(ehalogenation of Tetrahaloal.anes+
Tetrahaloalkanes on treating "ith actie metalsproduce alkynes. 'sually 9inc dust is used for delaogenation.
. At room temperature and pressure st three alkynes (i.e.from 5= to 5>) are colourless gases ne#t eight members i.efrom 5? to 5= are colourless liuids "hile alkynes from 5<
and on"ard are colourless solids.=. They are odourless e#cept ethyne "hich has garlic like
smell.<. The melting and boiling points of alkynes increase "ith
increase of molecular "eight.>. More is the number of branches in alkynes lo"er "ill be the
boiling points.?. Alkynes are insoluble in "ater but dissole freely in organic
solents like ether$ ben,ene$ carbon tetrachloride etc.
Structure of "l6)ne
Ethyne has triply bonded carbon atoms are sp hybridi,ed.The electronic configuration of carbon is s=$ =s=$ =p=. Itsalence shell has = electrons in s-orbital and one electron ineach of t"o p-orbitals "hile the third p-orbital is lying acant.
*y absorption of energy one of electron of =spromotes to acant p-orbital and atom becomes in e#citedstate$ "hich is not stable state. Thus to gain a state of stabilitymi#ing of atomic orbitals take place and energy is lo"ered./ne s-orbital and one p-orbital are mi#ed together and giet"o sp hybridi,ed orbitals. These t"o sp hybrid orbitals areidentical in shape and energy and each has a single electronin it. Also t"o unhybridi,ed p-orbitals each hae singleelectrons in it. !o carbon is tetraalent and not dialent.
The half filled s-orbitals of one hydrogen atom oerlap "ithhalf filled sp hybrid orbital of one carbon "hile half filled s-orbitals of other hydrogen atom oerlap "ith half filled sphybrid orbital of second carbon forming total t"o 5-7 sigma-bonds$ one "ith each carbon. As oerlapping hae takenplace on bond a#is so t"o 5-7 sigma bonds are produced.The t"o 5-7 sigma bonds are formed due to sp-soerlapping.
The remaining one sp hybrid of each carbon oerlaps amongthemseles on bond a#is thus forming 5-5 sigma bond. Thisbond is formed due to sp-sp oerlapping.The t"o unhybridi,ed p-orbitals (one of each carbon) areparallel to each other so they oerlap side "isely (i.e.laterally) and form pi-bond. !imilarly the other t"ounhybridi,ed p-orbitals (one of each carbon) are also parallelto each other so they also oerlap side "isely (i.e. laterally)
and form another pi-bond. The t"o pi-bonds are formed dueto p-p oerlapping. &i-bonds are "eek bonds and are easy tobreak hence ethyne is reactie.
Alkenes Z Alkynes Z AlkanesIt means that alkenes are most reactie in this series.
They hae a double bond "hich consists of a strong sigma() bond (bond energy K C< 4calmol) and a "eak pi ()-bond(bond energy K @< 4calmol). The density of -electrons is
high aboe and belo" the bond a#is. In other "ords -electrons are a"ay from the nuclei of the carbon atoms sohold of nuclei is less on them. Thus they are e#posed toelectrophilic attack. Thus an electrophile can easily attack andcan break bond by using less energy and therefore alkenesare more reactie. Alkynes are also reactie due to samereason but less than alkene. In alkynes electron densitybet"een t"o triply bonded carbon nuclei is more than that in
doubly bonded carbons in alkene so triple bond is shorter than double bond and hold of carbons nuclei on pi-electronsis more in alkynes and thus alkynes are less reactie thanalkenes.
Alkynes being unsaturated compounds mostly sho"saddition reactions. *eside addition reactions they also sho"o#idation reactions. An o#idi,ing agent can remoe their loosely bound -electrons.
The reactions of alkynes can be diided into four categories.
"D ddition ,eactions+
Alkynes being unsaturated compounds mostly sho"addition reactions and the addition is electrophilic addition.
Mechanism+
A polar or temporarily polari,ed molecule approachesto alkyne and e end of the molecule pulls its -electrons as
Addition of hydrogen is called hydrogenation.Molecular hydrogen cannot break -bond ho"eer atomic hydrogen can break it. Therefore to
dissociate molecular hydrogen intoatomic hydrogen either heating (from =>-<o5)is carried out in presence of 0ickel catalyst. If platinum catalyst is used then "ithout heatinghydrogen dissociates.
*ut if palladium poisoned by heay metal salt is used ascatalyst its catalytic ability is less hence concentration of atomic hydrogen "ill be less and hydrogenation "ill bestopped at production of alkene.
=. Halogenation+ Addition of halogens is called halogenation. It iscarried out in presence of 6erric chloride catalyst.7algenation of alkynes produces icinal tetrahaloalkanes.
If 5l= is taken in e#cess than =$=$<$<- tetrachlorobutane "ill be maPor product but if =-butyne is in e#cess then=$<- dichloro-=- butene "ill be maPor product.
5hlorine and bromine add readily "hile iodine reacts slo"ly.
Mechanism+
6erric chloride (catalyst) polari,es halogen i.e.chlorine or bromine.
The e end of the halogen molecule pulls -electrons and as a result halogen molecule breaks up ande halogen ion (chloronium or bromonium acts aselectrophile) forms a temporary bond "ith t"o multiplebonded carbons.
The elecrophile (halonium ion) makes permanent bond "ithone of the carbon and leaing e charge on other carbon.
The Fe ion (nucleophile i.e halide ion) attacks carbonium ionand offers its electrons to positiely charged carbon and
Addition of hydrogen and halogen is calledhydrohalogenation. 2hen alkynes are treated "ithhalogen acids hydrohalogenation take place. Incase of asymmetric alkynes addition follo"sMarko"nikoffSs rule. 7o"eer in case of symmetricalkynes only second addition is according toMarko"nikoffSs rule.The order of reactiity of halogen acids to"ardsthis reaction is
7I Z 7*r Z 75l Z 76
Mechanism+It follo"s same mechanism as in other addition
reactions of alkynes.
>. -ddition of Water Hydration#+2hen ethyne is treated "ith dilute (Q) 7=!/> in
presence of mercuric sulphate hydration occurs. Addition of "ater take place at about Co5. Inasymmetric alkynes Marko"nikoffSs rule isfollo"ed.
%inyl alcohol is unstable so it undergoes rearrangement toform aldehyde.
-l.ynes other than ethyne on hydration gi%e .etones
The unsaturated alcohol is unstable so it undergoes
rearrangement to form ketone..
BD /xidation ,eactions+
The -bond in alkynes is a "eak bond and .-electrons are loosely bound to carbon nuclei hence aresusceptible for the attack of o#idi,ing agents. Thereforeo#idi,ing agents can easily o#idi,e alkynes. !ome o#idationreactions of alkynes are follo"ing.
. Co"bustion+ Alkynes on burning produce 5/= and 7=/ apours
along "ith liberation of heat.This is o#idation reaction.
=. Oxidation by 12nO3+2hen alkynes are treated "ith dilute alkaline4Mn/> solution hydro#ylation of alkynes occursand as a result polyhydric alcohol is produced.
This A polyhydric alcohol is not stable so it undergoesdehydration to produce aldehyde.
4Mn/> further o#idi,es aldehyde to carbo#ylic acid.
This reaction could be used as identification for presence of carbon-carbon multiple bonds and is kno"n as ,aeyer+s test .Becolouri,ation of pink colour of 4Mn/> indicates thepresence of double or triple bond.
C. "ci$ic #eaction!+ All the terminal alkynes sho" acidic behaiour. In these
alkynes 7ydrogen is bonded to carbon due to sp-soerlapping. The sp-hybrid orbital has more s-character as compared to sp= and sp< hybrid orbitals. !o sp-hybridorbital is shorter and thus shared pair of electrons isshifted more to"ards carbon rendering more Fe charge
on it and conseuently more e charge on hydrogen ascompared to that in alkenes and alkanes. Therefore
terminal alkynes are capable of donating 7 ion (proton)and are acidic in nature. Alkynes other than terminalalkynes hae no hydrogen attached to sp-hybridi,edcarbon so they are not acidic.
!o terminal alkynes acting as acid donates proton (s) andreact "ith strong bases.
Alkynes are ery "eak acids$ "hich is clear from acidicstrength order gien belo"
7=/ Z 7557 Z 07<
!ome of the acidic reactions of alkynes are (i) 2hen terminal alkynes are treated "ith sodium
amide or potassium amide (strong bases) alkynesdonate proton and form acetylide or alkynides.
5 5- 7 0a07= 5 5- 0a
07<
Alkyne !odium amide !odium acetylide
5 5- 7 407= 5 5- 4
07<
Alkyne &otassium amide &otassium acetylide
Acetylides can be used for making higher alkynes. 5 5 0a 57<I 5 5 57< 0aI
(ii) /n passing terminal alkynes oer molten sodiumacid base reaction occurs and acetylides or alkynides are produced.
5opper and siler acetylides on reaction "ith dilutemineral acids reproduce alkynes
Ag 5 5 Ag 7=!/> (dil) 75 57 Ag=!/>
Ag 5 5 Ag =70/< (dil) 75 57 = Ag0/<
The reaction of terminal alkynes "ith ammonical cuprouschloride and ammonical siler nitrate could be used for identification of these alkynes. !e! of Eth)ne+
Ethyne is an important member of alkyne family and it hasmany uses.
. /n burning mi#ed "ith o#ygen gies o#yacetyleneflame "hich is used for "elding and cutting metals
=. It is used for artificial ripening of fruits.<. It is used for manufacturing of alcohol$ acetic acid and
acetaldehyde.
>. It is used for manufacture of polymers like poly inylchloride (&%5)$ poly inyl acetate (&%A)$ polyinylethers etc.
?. It is used for preparing acetylene tetra chloride "hichis a solent for arnishes$ resins and rubber.
@. It is used for making inyl acetylene "hich in turn isused for preparing synthetic rubber.
Ben+ene an$ Su!titute$ Ben+ene!
*en,ene "as first discoered by Michael 6aradey inC=?. !imilarly in C>? 7offmann found ben,ene in coaltar.Molecular formula of *en,ene has been found to be5@7@. This formula sho"s that ben,ene is highly
unsaturated compound haing four double bonds$therefore$ ben,ene should take > 7= molecules to becomecompletely saturated hydrocarbon. *ut in actual practiceben,ene takes < 7= molecules to become saturatedcompound. !imilarly ben,ene adds on < 5l= molecules tobecome saturated. Addition of < 7= or < 5l= suggests thatben,ene has < double bonds and not > double bonds. *utopen chain structure "ith < double bonds for ben,ene
does not satisfies the alency.It is further found that ben,ene gies only one monosubstituted compound "hich sho"s that all 7ydrogenatoms in ben,ene are euialent so no matter "hichhydrogen is replaced$ product "ill be the same.
These facts led 4ekule$ a German chemist in C@? togiecyclic structure for ben,ene. 7e suggested a
he#agonal ring for ben,ene "ith alternate double andsingle bonds bet"een carbons. Although 4ekule structure can e#plain many facts aboutben,ene but there are some obPections "hich cannot bee#plained by 4ekule structure e.g. according to 4ekulestructure "e should get t"o isomers of icinal di-substituted deriatie of ben,ene. In one isomer the t"o carbon atoms haing
substituents are linked through double bond "hile in =nd
isomer the carbons are linked through single bond. *ut inactual practice "e get only one icinal (or $=) di-substituted deriatie of ben,ene.
According to this theory each carbon in ben,ene is sp=
hybridi,ed. !o each carbon has three sp= hybridorbitals and one unhybridi,edp-orbital. The sp= hybrid orbitalsare coplanar haing an angle of
=o
bet"een them. 2hereas unhybridi,ed p-orbital isperpendicular to the plane of hybridi,ed orbitals. Each of sp= hybrid as "ell as unhybridi,edp-orbital has single electron in it.
/ne sp= hybrid orbital of each carbon oerlaps "ith s-orbitalof hydrogen$ on bond a#is forming 5-7 sigma bond "hileother t"o sp= hybrid orbitals oerlap "ith sp= hybrid orbitals
of t"o neighbouring carbons on the bond a#is forming 5-5sigma bond "ith each carbon. Thus si# carbons and si#hydrogen atoms form a coplanar he#agonal ring. *ond anglebet"een any t"o sigma bonds is =o
Each carbon has an unhybridi,edp-orbital "hich is at right angle toplane of he#agonal ring haing one
&lane. The p-orbitals are parallel to each other so each p-orbital oerlaps eually to the p-orbitals of t"o adPacentcarbons forming a special -bond system. The oerlapping islaterally i.e. -oerlapping. Each -electron is attractedeually by si# carbon nuclei$ therefore -bond in ben,ene is
delocali,ed -bond. As the lobe of p-orbitals are aboe andbelo" the plane of he#agonal ring so t"o electron clouds areformed aboe and belo". Thus ben,ene molecule resemblesa sand"ich$ the t"o electronic clouds are like t"o slices of bread and he#agonal ring is like meat etc bet"een slices.
Molecular orbital picture of ben,ene can e#plain all theproperties of ben,ene "hich other"ise could not be e#plained
on the basis of 4ekule or other structures. As each -electronis attracted by si# carbon nuclei so it is ery much resistant too#idi,ing agents and same is the reason for not occurrence of addition reactions in ben,ene. 6urther according to thispicture all carbons are euialent and bond length of any 5-5
bond is .<HAo. This picture also account for lo"er energy
than the one calculated by 4ekule structure. The difference
bet"een energy of molecular orbital structure of ben,ene and4ekuleSs structure is called delocali,ation energy and it is<@kcalmol or ?kLmol. It is same as is resonance energy.
As delocali,ation energy is high so ben,ene is stable. In shortmolecular orbital picture is best description of ben,eneSsstructure.
,esonance heory $
According to this theory some molecules are represented byt"o or more structures and the actual structure is hybrid and"eighed aerage of these. There are certain molecules "hichcannot be represented by single structure$ so "e "rite
arious possible structures for such molecules. Thesepossible structures are called resonating structures. The realstructure is "eight aerage of these resonating structures andis called resonance hybrid.
Each resonating structure contributes to real structure. !omestructures contribute more (MaPor contributors) and other contributes less (Minor contributors). More is the stability of aresonating structure more is its contribution to resonance
hybrid (real structure). All structures proposed for ben,ene by different peoplecontributes but 4ekuleSs structures are maPor contributing
structures
for resonance hybrid of ben,ene. 4ekuleSs structures contribute about CQ toresonance hybrid.
It should be clear in mind that neither half ben,ene moleculeshae one 4ekuleSs structure and half hae other nor ben,enemolecules hae for some time one structure and for some
time other structure. *ut in fact all ben,ene molecules haeonly one structure for all the time and that is resonancehybrid. The resonance hybrid is imaginary structure "hich isobtained by mental combination of resonating structures.Greater is the contribution of resonating structure more is itsresemblance "ith resonance hybrid.
The resonance hybrid is al"ays lo"er in energy than
resonating structures$ therefore$ it is stable. The difference inenergy of resonance hybrid and that of most stableresonating structures (4ekuleSs structures) is calledresonance energy. This resonance energy is the same as isdelocali,ation energy in Molecular orbital theory. esonance
energy of ben,ene is <@ k calmol or ? kLmol$ "hich ishigh and thus ben,ene is stable compound.
Stailit) of Ben+ene:
*en,ene has e#traordinary stability and it is due todelocali,ation of pi-bonds.5yclohe#ane is "hen hydrogenated to get cyclohe#ane$ =C.@kcalmol or H.? kLmol heat is liberated.
7= ] 7 K -=C.@ kcalmol or -H.? kLmol
$<-5yclohe#adiene is "hen hydrogenated to getcyclohe#ane$ double amount of heat is liberated.
=7= ] 7 K -?.> kcalmol or -=<H kLmol
$<$?-5yclohe#atriene is "hen hydrogenated to getcyclohe#ane$ triple amount of heat is liberated.
<7= ] 7 K -C?.C kcalmol or -<?C.? kLmol
*ut "hen *en,ene is hydrogenated$ >H.C k calmol or =CkLmol heat is liberated. It means that ben,ene sho"s <@
kcalmol or ? kLmol less energy than e#pected. The lo"erheat of hydrogenation of ben,ene than the calculated one isthe cause of stability of ben,ene and is called resonanceenergy
<7= ] 7 K ->H.C kcalmol or -=C kLmol
Preparation,E.traction of Ben+ene+
*en,ene is obtain by t"o natural sources and can also beprepared from acetylene.
0ro" Coal +5oal is a black color mineral found under earth crust. It is ami#ture of organic and in organic substances. Its destructiedistillation gies four fractions. Then on fractional distillation of coal tar again four fractions are obtained. These are sho"nbelo". 5oal tar contains about .@Q ben,ene and about .?Qhomologues of ben,ene.
ight oil contains *en,ene. 6urther fractional distillation giesben,ene and its homologues.
*en,ene obtained from light oil is Q pure and is suitable for commercial use but for analytical purposes its purification isneeded.
&urification of ben,ene+ 6or this purpose ben,ene is fro,en at
? o5$ mostly impurities are left as liuid and are remoed byfiltration. *ut still sulphur impurities kno"n as thiophenes areleft. *en,ene is again liuefied and is mi#ed "ithconcentrated sulphuric acid and is shaken "ell. The sulphur impurities are get dissoled in the acid. The mi#ture onstanding separates into t"o layers "hich are separated byseparating funnel.
Ph)!ical Propertie! of Ben+ene+(i) *en,ene is a colourless liuid.(ii) It has a characteristic smell.
(iii) Its boiling point is C o
5 and melting point is ?.?o5.
(i) Its density is .CH gcm<
.() It is immiscible "ith "ater.(i) It is highly flammable.(ii) It is a good organic solent.
Cheical Propertie! of Ben+ene+
*en,ene like alkanes is less reactie. It is difficult to
break its pi bond system. Mostly reactions of ben,ene likethat of alkanes are electrophilic substitution reactions. Also itso#idation at ordinary conditions is ery difficult. In electrophilicsubstitution reactions its aromaticity is retained ho"eer ino#idation$ reduction and addition reactions its aromaticity islost.
eactions of ben,ene are diided into four categories.
(A) "lectrophilic Substitution reactions+
Electron loing species or reagent is calledelectrophile. It could be some cation or a molecule "hich is
electron deficient e.g. 7$ 0/=$ $ <5$ 7!/<
$ 57<5/$ Al5l< etc.
Electron donating species or reagent is callednucleophile e.g. 50-$ 8-$ /7-$ -/$ -!$ 7 F 5 ? 5-$ 07<$7=/ etc.
*en,ene and other aromatic compounds mostly sho"selectrophilic substitution reactions. Electrophilic substitutionreactions in ben,ene take place through follo"ing mechanisminoling three steps.
!tep-I Generation of strong electrophile+/nly strong electrophile can attack the -electrons of ben,ene and cations are strong electrophiles.Therefore catalysts are used to dissociate reagent
molecules for producing cations.
E F 0u 5 8 E 5 F 0u-
!tep-II Attack of Electrophile on Aromatic ing+
In this step electrophile attacks the aromatic ringproducing phenonium ion. The positie charge on phenoniumion is delocali,ed oer the ben,ene ring thus the ion is stable.7o"eer this ion is less stable than aromatic ring.6urthermore this ion is non aromatic.
!tep-III+ Approach of 0ucleophile2hen nucleophile approaches phenonium ion then
there are t"o possibilities of giing final product.
(a) /ne possibility is that nucleophile gets attached tophenonium ion and gies addition product.
(b) !econd possibility is that phenonium gie a protonand form aromatic compound.
6or phenonium ion$ it is energetically more preferable tolose proton to gie an aromatic substitution product thanto gie a non-aromatic addition product. Thus this reaction"ill occur.
(i) Nitration+
*en,ene on reaction "ith conc 70/< at ?-@o5
in presence of sulphuric acid produces 0itro ben,ene.
0itration of ben,ene gies mono substituted product.
Mechanism+
!tep-I Generation of strong electrophile+0itric acid on reaction "ith sulphuric acid producesnitronium ion "hich act as strong electrophile.
7/-
F 0/=
7
F-
/!/=/7 80/=
-/!/=/7 7=/
!tep-II Attack of Electrophile on Aromatic ing+
In this step electrophile (0/=) attacks the aromatic
ring producing phenonium ion. The positie charge onphenonium ion is delocali,ed oer the ben,ene ring thus theion is stable. 7o"eer this ion is less stable than aromatic
!tep-III+ Approach of 0ucleophile or emoal of proton
2hen nucleophile (-/!/=/7) approachesphenonium ion it gies a proton and form
nitroben,ene. 2hile sulphuric acid i.e. catalyst isreproduced.
(ii)alogenation+
*en,ene reacts "ith halogens in t"o different "aysunder t"o different conditions i.e. in presence of directsunlight and in diffused sunlight using catalyst.
2hen ben,ene is treated "ith halogens inpresence of 6e*r < or Al5l< it gies substitution product i.e.halo ben,ene.
7alogenation of ben,ene gies mono substituted product.
Mechanism+
!tep-I Generation of strong electrophile+5hlorine on reaction "ith Al5l< produces 5hloroniumion "hich act as strong electrophile.
5l F 5l-
Al5l< 8 5l Al5l>-
!tep-II Attack of Electrophile on Aromatic ing+
In this step electrophile (5l) attacks the aromatic ringproducing phenonium ion. The positie charge on phenoniumion is delocali,ed oer the ben,ene ring thus the ion is stable.
7o"eer this ion is less stable than aromatic ring.6urthermore this ion is non aromatic.
!tep-III+ Approach of 0ucleophile2hen nucleophile (Al5l>-) approaches phenonium ion it giesa proton and form 5hloro ben,ene. 2hile Al5l< i.e. catalyst isreproduced.
(iii) Sulphonation+*en,ene reacts "ith fuming sulphuric acid and
gies ben,ene sulphonic acid$ the process is calledsulphonation.
!ulphonation of ben,ene gies mono substituted product.
Mechanism+
!tep-I Generation of strong electrophile+!ulphuric acid molecule dissociates in presence of other molecule to produce cation "hich act as strongelectrophile.
aromatic ring producing phenonium ion. The positie chargeon phenonium ion is delocali,ed oer the ben,ene ring thusthe ion is stable. 7o"eer this ion is less stable than aromatic
ring. 6urthermore this ion is non aromatic.
!tep-III+ Approach of 0ucleophile
2hen nucleophile (7/!/=/-) approachesphenonium ion it gies a proton and form ben,ene
sulphonic acid.
(i) 4rie$el-Craft! #eaction!+
The alkylation and acylation of ben,ene are called6riedel 5rafts reactions.
(a) -l.ylation+
2hen ben,ene is treated "ith alkyl halide inpresence of 6e*r < or Al5l< it gies substitution product i.e.
Alkylation of ben,ene does not stop at the stage of monoalkylation rather further alkylation "ill occur.
Mechanism+
!tep-I Generation of strong electrophile+ Alkyl halide on reaction "ith Al5l< produces 5aboniumion "hich act as strong electrophile.
57< F 5l- Al5l< 8 57< Al5l>-
!tep-II Attack of Electrophile on Aromatic ing+
In this step electrophile (57<) attacks the aromatic
ring producing phenonium ion. The positie charge on
phenonium ion is delocali,ed oer the ben,ene ring thus theion is stable. 7o"eer this ion is less stable than aromaticring. 6urthermore this ion is non aromatic.
!tep-III+ Approach of 0ucleophile
2hen nucleophile (Al5l>-) approaches phenonium ion it giesa proton and form Alkyl ben,ene. 2hile Al5l< i.e. catalyst isreproduced.
2hen ben,ene is treated "ith acyl halide inpresence of 6e*r < or Al5l< it gies substitutionproduct i.e. aromatic ketone.
Acylation of ben,ene gies mono substituted product.
Mechanism+
!tep-I Generation of strong electrophile+
Acyl halide on reaction "ith Al5l< produces acyliumion "hich act as strong electrophile.
!tep-II Attack of Electrophile on Aromatic ing+In this step electrophile (57<5/) attacks the
aromatic ring producing phenonium ion. The positie chargeon phenonium ion is delocali,ed oer the ben,ene ring thusthe ion is stable. 7o"eer this ion is less stable than aromaticring. 6urthermore this ion is non aromatic.
2hen ben,ene is strongly heated "ith air inpresence of anadium o#ide catalyst it o#idi,es tomaleic anhydride. In this reaction aromatic ring isdestroyed.
The maleic anhydride on reaction "ith "ater
produces maleic acid.(5) ddition ,eactions+
*en,ene sho"s only fe" addition reactions.
(i) )$rogenation+
2hen ben,ene is treated "ith hydrogenaddition of hydrogen takes place andaromaticity is lost.
&t
<7= 0i :=o
5;
5yclohe#ane(ii) alogenation+2hen ben,ene is treated "ith 5l= or *r = inpresence of direct sunlight addition of thesehalgens take place and aromaticity is lost.
2hen ben,ene is treated "ith hydrogen itsreduction occurs due to addition of hydrogen
and aromaticity is lost. &t
<7= 0i :=o
5;5yclohe#ane
"!!ect o! a Substituent on !urther Substitution:
A substituent present on aromatic ring influencesfurther substitution in t"o "ays() /rienting effect (=) Effect on reactiity of ben,ene ring
10 /rienting "!!ect or +irecti#e In!luence
If a substituent is already present on ben,ene ring$
then it directs the ne#t coming group to a particular position on the aromatic ring. It could be proed by ane#periment.If "e perform nitration of ben,ene first and thenchlorination "e get m-5hloro 0itro *en,ene.
/n other hand if "e perform chlorination of ben,ene first andthen nitration "e get o-5hloro 0itro *en,ene and p-5hloro0itro *en,ene.
Nitro Ben+ene
This e#periment sho"s 0itro group sends the ne#t group tometa position "hile 5hloro group sends the ne#t group toortho and para positions. Thus "e can diide the substituentof ben,ene into t"o categories meta Forienting groups andorto-para orienting groups
/rtho-&ara /rienting Groups Meta-/rienting Groups. -/7 (actiating group) . -0/=
'sually in meta-orienting groups the key atom is either multiple bonded to another atom or it is positiely charged.
10 "!!ect on ,eacti#ity /! $enene ,ing
The reactiity of ben,ene ring is affected by presenceof a substituent on the ring. 'sually orto-para orientinggroups e#cept halogens increase the reactiity of thering and are hence called actiating groups. /n other hand meta Forienting groupsdecrease the reactiity of the ring so they are termed
as deactiating groups.
This can be proed by a simple e#periment.
0itration of ben,ene occurs at ?-@o5
!econd nitro group can only be introduced on ery strongheating because the already present nitro group beingdeactiating group decreases the reactiity of ring so
introduction of second nitro group become difficult.
/n other hand nitration of Toluene occurs at <->o5$ at
@-o5 t"o nitro groups get attached to the ring and at
o5 een three nitro groups get attached to the ring. !o
nitration of toluene is easier than that of ben,ene.
These reactions sho" that nitration of toluene is een easier than ben,ene. This is due to the reason that already presentmethyl group being actiating group increases the reactiity of ring so nitration of toluene become easier.
/rtho-para orienting groups are electron sending groups$ so
they send electrons to the aromatic ring due to "hichnegatie charge appears on ortho and para positions assho"n belo".
Bue to appearance of negatie charge on ortho andpara positions$ the aailability of electrons on theseposition become more than that on meta position.Befinitely electrophile attacks "here aailability of electrons is more thus it attacks on ortho and parapositions.
6urthermore ortho-para orienting groups increase the
reactiity of aromatic ring. The reactiity of the ringincreases due to t"o reasons.
(i) /rtho-para orienting groups being electronsending groups send electrons to the ring andincrease the aailability of electrons on the ringso the approach of electrophile to ringbecomes easy and hence reactiity increases.
(ii) &resence of ortho-para orienting groups on thering increase the stability of intermediatephenonium ion thus reactiity increases.
Meta orienting groups are electron puling groups$ sothey pull electrons from the aromatic ring due to "hich
positie charge appears on ortho and para positionsas sho"n belo".
Bue to appearance of positie charge on ortho andpara positions$ the aailability of electrons on theseposition become less than that on meta position.Befinitely electrophile attacks "here aailability of electrons is more thus it attacks on meta position.
6urthermore meta orienting groups decrease thereactiity of aromatic ring. The reactiity of the ringdecreases due to t"o reasons.
(i) Meta orienting groups being electron pullinggroups pull electrons from the ring anddecrease the aailability of electrons on thering so the approach of electrophile to ring
becomes difficult and hence reactiitydecreases.
(ii) &resence of meta orienting groups on the ringdecreases the stability of intermediatephenonium ion thus reactiity decreases.
6ollo"ing are fe" methods of preparation of alkylhalides.
i) ,y Halogenation of al.anes+
Alkanes on treating "ith halogens in presence of
sunlight or heating at >o5 gies a mi#ture of haloalkanes. e.g.>57> >5l= '% 57<5l 57=5l= 575l< 55l> >75l*ut this method is oftenly not used because it isdifficult to separate mi#ture of haloalkanes.
ii) ,y Hydrohalogenation of -l.enes+
The addition of halogen acids is calledhydrohalogenation. 7ydrohalogenation of alkenesproduce alkyl halides. The order of reactiity of halogen acids to"ards this reaction is
7I Z 7*r Z 75l Addition of halogen acids to alkenes follo"s
Marka"nikoffSs rule.
7ere addition took place according to Marko"nikoffSs rule.
Alcohols on reaction "ith thionyl chloride$ producecorresponding alkyl chlorides.
#eacti(it) of "l6)l ali$e!+
Bon$ Energie!: To understand the reactiity of alkyl halidesin terms of bond energies. etSs look at the table+
Bon$ Bon$ energ) Bon$ Bon$ energ)
5-6 >@ kP mol 5-*r =H kP mol
5-7 >< kP mol 5-I ==C kP mol5-5l <>@ kP mol
• The 5 F 6 bond is highly polar so is stronger bondand is difficult to break on other hand 5 F I bond isless polar and is less stronger so easily can bebroken. The electronegatiity difference of halogens"ith carbon decreases from fluorine to iodine thusbond strength decreases as a result reactiityincreases. Therefore order of reactiity of alkylhalides is
F I Z F *r Z F 5l Z F 6
• The reactiity of alkyl halides also depend uponnature of alkyl group such that
one molecule is inoled in rate determining step thereaction is called unimolecular reaction$ if t"o moleculesare inoled then it is called bimolecular reaction$ for more than t"o molecules reaction is called polymolecular reaction.
ate of 0ucleophilic !ubstitution eactions+ The rate of these reactions depends-on+
. 0ature of the substrate (Alkyl halide)=. 0ature of the attacking nucleophile<. 0ature of the leaing nucleophile>. 0ature of the solent
2echanis" of Nucleophilic Reactions+
Alkyl halides may undergo nucleophilic substitution
reactions in t"o different "ays.(i) 'nimolecular 0ucleophilic !ubstitution eactions
(!0
mechanism).
(ii) *imolecular 0ucleophilic !ubstitution eactions (!0=
mechanism).
(i) niolecular Nucleophilic Su!titution #eaction!
'SN1
echani!*+
This mechanism inoles t"o steps.
!tep-IIn this step formation of carbonium ion takes
place. The alkyl halide molecule dissociates toproduce carbonium ion. This is energy absorbing stepand is slo" step.
!tep-IIIn this step nucleophile attacks carbonium ion
from either side i.e from side from "hich halide hasgone or from opposite side "ith eual ease. Asleaing group had already gone$ also the carboniumion thus formed is planar so it allo" the nucleophile toattack on it from both sides "ith eual ease. 2e$
thereforeobsere ?Q inersion of configuration and?Q retention of configuration. This is bond formation step so energy is released andis fast step.
As only one molecule is inoled in rate determining step(slo" step) so molecularity of the reaction is one and thusreaction is unimolecular nucleophilic substitution reaction.
The rate of reaction depends only upon concentration of alkylhalide and not on that of nucleophile.ate j :alkyl halide;
Tertiary alkyl halide sho"s this mechanism. e.g. consider hydrolysis of tertiary butyl bromide.
!tep-I
The tertiary butyl bromide molecule dissociates to producecarbonium ion. This is energy absorbing step and is slo"step.
In this step nucleophile i.e /7- attackscarbonium ion from same side from "hich bromide ionhas gone. In this step energy is released and is faststep.
(ii) Biolecular Nucleophilic Su!titution #eaction!
'SN9
echani!*+
This is a single step mechanism. In this mechanism bondbreaking and bond formation take place simultaneously. Assoon as nucleophile starts attacking the electrophilic carbonof the substrate (alkyl halide)$ leaing group starts breakingits bond at the same moment.
0ucleophile attacks from the side opposite to the leainggroup. In order to gie enough room to nucleophile for itsattack$ the electrophilic carbon of substrate changes itshybridi,ation from tetrahedral sp< to planar sp=.
Buring reaction inersion of configuration takes place.
. It is t"o step reaction.=. It is unimolecular reaction.<. ate of reaction dependsonly on concentration of alkyl halide.ate j :alkyl halide;
>. ate depends on thestructure of alkyl halides inthe follo"ing order Ter 8 Z!ec 8 Z &ri 8
?. eaction is faoured bypolar solents.
polar solents.@. eaction usually occurs"ith "eak bases.. 5arbonium ion formationtake place.C. 0ucleophile can attackfrom any side.
H. There are ?Q chancesof inersion of configuration.
. It is one step reaction=. It is bimolecular reaction.<. ate of reaction dependsboth 'pon concentration of alkyl halide as "ell asnucleophile ate j :alkylhalide; :nucleophile;
>. ate depends on thestructure alkyl halides inthe follo"ing order &ri8 Z !ec 8 Z Ter 8?. eaction is faoured bynon@. eaction usually occurs"ith strong bases.
Some o! important nucleophilic substitution reactions o! al.yl halide+
.Reaction with a4ueous 1OH
+ Alkyl halide on treating "ith aueous potassium hydro#ide$sho" substitution reaction and produce correspondingalcohol
Ethyl bromide is primary alkyl halide so it "ill follo" E=
mechanism.
%rignar$H! #eagent '# I Mg I 5*:
These are organo metallic compounds. They are eryreactie and are important for synthesis of organiccompounds. They are called alkyl magnesium halides. Preparation+
They are prepared by heating alkyl halide andmagnesium in presence of completely anhydrous ether.
Alkyl halide$ magnesium metal and dry ether are taken in around bottom flask. The flask is fitted "ith a "ater condenser carrying a guard tube. The guard tube contain 5a5l= in it"hich absorbs moisture. The flask is heated in a "ater bath.
eaction of GrignardSs reagent "ith aldehydesfollo"ed by acid hydrolysis produces primary or secondary alcohol.
(a) eaction "ith 6ormaldehyde+eaction of GrignardSs reagent "ithformaldehyde follo"ed by acid hydrolysisproduces primary alcohol haing one morecarbon than that of grignardSs reagent.
(b) eaction "ith Aldehydes other than6ormaldehyde+eaction of GrignardSs reagent "ith aldehydes other
than formaldehyde follo"ed by acid hydrolysis producessecondary alcohol.
#eacti(it) of "ine!: Amines are reactie mainly due to the presence of lone pair of nitrogen atom. This lone pair of electron is aailable to theelectrophile (electron pair deficient specie). /n the basis of
this lone pair amines act as nucleophile in nature. These areimportant organic compounds. Amines react "ith no of different molecules to produce aluable compounds.
1D #eaction of "onia /ith "l6)l ali$e!:
The reaction of alkyl halides "ith alcoholic solution of ammonia to produce amines is called ammonolysis or
7offmann reaction. /n heationg mi#ture of ammonia andalkyl halide$ alkylation of ammonia occurs and mi#ture of amines is obtained.
In the first stage$ the ammonia reacts "ith the ethanoylchloride to gie ethanamide and hydrogen chloride gas.
Then the hydrogen chloride produced reacts "ith e#cessammonia to gie ammonium chloride.
. . . and you can combine all this together to gie one oeralleuation+
Ma6ing ai$e! fro aci$ anh)$ri$e!
An acid anhydride is "hat you get if you remoe a moleculeof "ater from t"o carbo#ylic acid -5//7 groups.
6or e#ample$ if you took t"o ethanoic acid molecules andremoed a molecule of "ater bet"een them you "ould getthe acid anhydride$ ethanoic anhydride (old name+ aceticanhydride).
The reactions of acid anhydrides are rather like those of acylchlorides e#cept that during their reactions$ a molecule ofcarbo#ylic acid is produced rather than the 75l formed "henan acyl chloride reacts.
If ethanoic anhydride is added to concentrated ammoniasolution$ ethanamide is formed together "ith ammoniumethanoate. Again$ the reaction happens in t"o stages.
In the first stage$ ethanamide is formed together "ith ethanoicacid.
Then the ethanoic acid produced reacts "ith e#cess ammoniato gie ammonium ethanoate.
. . . and you can combine all this together to gie one oeralleuation+
Preparation of 0i-a+oniu Salt:
2hen primary aliphatic amines are treated "ith nitrous acid$
they produce highly unstable salts called as dia,onium salt.The solution of phenylamine in hydrochloric acid(phenylammonium chloride solution) is stood in a beaker ofice. The sodium or potassium nitrite solution is also cooled inthe ice.
The solution of the nitrite is then added ery slo"ly to thephenylammonium chloride solution - so that the temperature
neer goes aboe ?O5.
Uou end up "ith a solution containing ben,enedia,oniumchloride+
There are t"o important members of alcohol family and theyare methyl alcohol and ethyl alcohol.
n$u!trial Preparation of Meth)l "lcohol+
0ames+ Methyl alcohol$Methanol $ 2ood spirit
(5ommon system) (I'&A5 system) Methanol can be prepared by follo"ing methods.
. *y Bestructie distillation of 2ood+
2hen "ood is heated at >->?o5 in absence of air (destructie distillation)$ three fraction are obtained. Thesefractions are gaseous fraction$ liuid fraction (&yro-
ligneous acid) and tar. The liuid fraction contains <-?Qmethanol and Q ethanoic acid. *y fractional distillationof liuid fraction methanol is obtained.
Alcohols are "eak acids so they react "ith sodium metal"hich act as base and produce ionic compound alko#ide andhydrogen gas is liberated.
7o"eer alcohols are "eak acids "ith 4a alues of -@ to-C. The alkyl group in alcohols release electrons to o#ygenatom$ "hich increases its partial negatie charge hence itbecomes difficult to release proton. That is the reasonalcohols are less acidic than "ater.
Preparation of "lcohol!:
)$rol)!i! of "l6)l ali$e! Alkyl halide on treating "ith aueous potassium hydro#ide$sho" substitution reaction and produce correspondingalcohol.
Mechanism+Ethyl bromide is primary alkyl halide so it "ill follo"
As acid is replaced by "ater so actually addition of "ater hastaken place$ therefore$ the reaction is called Hydration ofalkenes.
#eaction of %rignar$H! #egent /ith "l$eh)$e an$Ketone:2hen al$eh)$e! are treated "ith grignad reagents follo"edby acid hydrolysis$ primary or secondary alcohols are
produced. (a) eaction of 6ormaldehyde+
eaction of formaldehyde "ith GrignardSs reagents$ follo"edby acid hydrolysis produces primary alcohol haing one morecarbon than that of grignardSs reagent.
(b) eaction of Aldehydes other than 6ormaldehyde+eaction of aldehydes other than formaldehyde "ithGrignardSs reagents$ follo"ed by acid hydrolysis producessecondary alcohol.
2hen 6etone! are treated "ith grignad reagents follo"ed byacid hydrolysis$ tertiary alcohols are produced.
#e$uction of "l$eh)$e! an$ Ketone!:
2hen al$eh)$e! are treated "ith hydrogen in presence of &tor 0i catalyst addition of hydrogen (hydrogenation) take placeand corresponding primary alcohols are produced.
2hen Ketone! are treated "ith hydrogen in presence of &t or 0i catalyst addition of hydrogen (hydrogenation) take placeand corresponding secondary alcohols are produced.
Tertiary alcohol Z secondary alcohol Z primary alcohol
The order of reactiity of alcohols "hen / 7 bond fissiontake place.
&rimary alcohol Z secondary alcohol Z tertiary alcohol
eactions of alcohols are diided into follo"ing categories+
(A) Reactions in which O 5 H bond fission ta.e place+
#eaction /ith caro.)lic "ci$ 'E!terification*:
2hen alcohol is treated "ith 5arbo#ylic acid in presence of conc sulphuric acid$ ester is produce. !ulphuric acid absorbs"ater and stops reerse reaction.
(*) Reactions in which C 5 O bond fission ta.e place+
1D #eaction /ith alogen aci$!
Alcohols react "ith halogen acids to produce alkyl halide and"ater.
/rder of reactiity of this reaction depends both upon natureof alcohol as "ell as halogen acids.
Tertiary alcohols Z !econdary alcohols
Z &rimary alcohols 7I Z 7*r Z 75lThis reaction can be used to distinguish bet"een pri$ sec andter- alcohols and is called ucas reagent test.
'ucas ,eagent est :
A mi#ture of conc 75l and anhydrous 9inc chloride is
called ucas eagent. 2hen an alcohol is treated "ith thismi#ture corresponding alkyl halide is produced "hich isinsoluble so causes turbidity.Tertiary alcohols react rapidly and produce alkyl halide sothey gie turbidity immediately.!econdary alcohols gie turbidity "ithin ?- minutes.
=?o5$ in presence of Al=/< and ethers are produced.
Clea(age of 1>9-$iol! '%l)col!*:Ethylene glycol "hen treated "ith 4Mn/> (acidic) or &otassium di chromate $ results in the formation of methanoicacid due to the cleaage of carbon-carbon bond.
The Sulpher "nalogue! 'Thiol! #S*:*oth /#ygen and !ulpher belongs to the same group of periodic table (%I-A). There are sulpher analogue of alcoholsand ethers in "hich sulpher is present instead of o#ygenatom.
-/7------!7 -/------- -!-The sulpher analogue of alcohols are called Thiols or Mercaptanes. The functional group of thiol is F!7. This iscalled suphydryl or marcapto. 2hen they react "ith mercuricsalts they form insoluble salts kno"n as mercaptanes.
•
Methane thiol is a gas• Ethan thiol and higher members of this groupare colorless$ olatile liuids at !T&.
• o"er members hae strong repulsie odors. Itis added in natural gas to detect the gasleakages.
• Thiols hae lo"er boiling point thancorresponding alcohols due to lack of hydrogen bonding$ due to "hich they areinsoluble in "ater but soluble in organicsolents.
!odium pheno#ide is then made to react "ith 75l to obtain&henol.
Structure of Phenol!:
The hydro#yl group isattached to ben,enering. The molecule isplaner$ the 5-/-7 bondangle is H$ "hich isalmost the same as that
of tetrahedral structure.In phenol all the si#carbon atoms are sp= hybridi,ed. In alcohol the 5-/ bondlength is .>=A "hile in phenol this length is .<@A the reasonis hybridi,ation is !&= in phenol and !&< in alcohol.
Ph)!ical Propertie! of Phenol+
(i) &henol is a colourless crystalline solid.(ii) It has a ery characteristic odour.(iii) It is deliuescent solid.
(i) It is lo" melting solid. Its melting point is >o5.
() It boils at C= o5.(i) It is poisonous.(ii) It is sparingly soluble in "ater at room temperature
but aboe @C.? o5 it become completely soluble.(iii) It is a "eak acid.(i#) It has corrosie action for skin.
The reaction of phenol can be diided into t"o categories.
(A) eactions due to functional group D/7+ (i) "ci$ic Beha(iour:
&henol is a "eak acid than carbo#ylic acids but stronger acidthan "ater and alcohols.
5arbo#ylic acids Z &henol Z 2ater Z AlcoholsIts acid dissociation constant (4a) is .< # -. Its p7 is ?-@.
In aueous solution it furnishes proton (7 ion) andpheno#ide ion. Its acidic nature is due to stable pheno#ideion. The stability of pheno#ide ion is due to resonance. Thenegatie charge
spreads oer the ring and become delocali,ed. Bue todelocali,ation of negatie charge$ the pheno#ide ion becomesstable. /n the other hand negatie charge of alko#ide ion of alcohol is not delocali,ed so alko#ide ion is less stable andthus alcohol is much less acidic than phenol.
&henol being acid reacts "ith alkalis to produce salt and"ater.
The 5 F / F 5 linkage is ery strong and not easy to break sothey are inert. Therefore they do not react "ith o#idi,ingagents $ reducing agents$ bases$ sodium etc at ordinaryconditions. 7o"eer they react "ith acids as they possesslone pair of electrons "hich they can offer to acids.
'i* #eaction /ith Cl an$ Br 'foration of
O.oniu Salt*:
/n reaction "ith these halogen acids they produce di alkylo#onium halides.
'ii* #eaction /ith Sulphuric aci$:
/n reaction "ith sulphuric acids they produce alkyl o#oniumhydrogen sulphate.
(a) *y o#idation of secondary alcohols+ Acetone and other ketones are produced by o#idation ofsecondary alcohols "ith strong o#idi,ing agents like chromicmi#ture.
(b)(b)(b)
*y 7ydration of Alkynes+
Alkynes other than Ethyne on hydration gie ketones.
unhybridi,ed p-orbital oerlaps "ith p-orbital of o#ygen andforms pi () bond. The carbonyl group is planar haing bond
angles of about =o.
*ond bet"een carbon ando#ygen are both polar and unsaturated so aldehydes andketones are reactie. 5arbon can be attacked by nucleophilesand o#ygen can be attacked by electrophiles but nucleophilicattacks are more prominent.
Aldehydes and ketones beside other reactions also sho"nucleophilic addition reactions.
The carbon and o#ygen atoms in the carbonyl group ispresent in aldehyde and ketones$ "hich consists of onesigma and one pi bond. *oth carbon and o#ygen are !&=hybridi,ed. The three atoms attached to carbonyl carbon lie inthe plane "ith bond angle of =. There are still t"ounshared electron pairs on o#ygen atom. The 5K/ bonddistance is .=<A$ shorter than 5-/ bond distance in alcohols"hich is .>< A.
Nucleophilic "$$ition #eaction: Aldehydes and 4etones mainly undergoes 0u additionreaction due to presence of unshared electron . Thesereaction may be either acid cataly,ed or base cataly,edreactions.
'i* "ci$ Catal)+e$ "$$ition #eaction:Bue to presence of unshared electron pair on
o#ygen$ carbonyl compounds are "eak le"is bases and canbe protonated. Acid can cataly,ed the addition of "eaknucleophiles to carbonyl compounds by protonating the
As alkyl group is electron donor compared to hydrogen. Theytend to neutrali,e the partial positie charge on carbonylcarbon$ and decreases its reactiity to"ards nucleophilicattacks. 4etones hae such alkyl groups "hile aldehyde haeonly one.
Ph)!ical Propertie!+ Aldehydes+
(i) o"er aldehydes are colourless liuids e#ceptformaldehyde. 6ormaldehyde is a colourless gas.(ii) o"er aldehydes hae unpleasant pungent smell.6ormaldehyde has suffocating odour.
(iii) Aldehydes are polar compounds so they hae highboiling points than corresponding alkanes but lo"er thancorresponding alcohols as they hae no hydrogen bond intheir molecules.(i) Bensity of aldehydes is less than "ater.() o"er aldehydes are soluble in "ater due toformation of hydrogen bond "ith "ater "hile higher memberscontaining more than fie carbons are insoluble in "ater.
4etones+
(i) o"er ketones are colourless liuids. Aromaticketones are solids.(ii) o"er ketones hae pleasant s"eet smell.(iii) 4etones are polar compounds so they hae highboiling points than corresponding alkanes but lo"er than
corresponding alcohols as they hae no hydrogen bond intheir molecules.(i) Bensity of ketones is less than "ater.() o"er ketones are soluble in "ater due toformation of hydrogen bond "ith "ater "hile higher
members containing more than fie carbons are insoluble in"ater.
Cheical Propertie!+
. -ddition Reactions+ Aldehydes and ketones sho" nucleophilic additionreaction on carbonyl group.
(i) Cleen!on #e$uction+2hen al$eh)$e! are treated "ith hydrogen inpresence of 9n-7g called as ,inc amalgamcatalyst addition of hydrogen (hydrogenation) takeplace and corresponding alkanes are produced.
2hen Ketone! are treated "ith hydrogen inpresence of &t or 0i catalyst addition of hydrogen(hydrogenation) take place and correspondingsecondary alcohols are produced.
'ii*olf-Ki!hner #e$uction:
"hen aldehyde or ketone is heated "ith hydra,ine$ acorresponding hydra,one is obtained$ "hich on heating "ith4/7 in boiling ethylene glycol gie the corresponding
and corresponding cyanohydrins are produced. This is a basecataly,ed addition reaction.
2hen Ketone!are treated "ith hydrogen cyanide in presence of baseaddition of hydrogen cyanide take place and correspondingcyanohydrins are produced. This is a base cataly,ed additionreaction.
2hen al$eh)$e! are treated "ith grignad reagents follo"edby acid hydrolysis$ primary or secondary alcohols areproduced.
(a) eaction of 6ormaldehyde+
eaction of formaldehyde "ith GrignardSs reagents$ follo"edby acid hydrolysis produces primary alcohol haing one morecarbon than that of grignardSs reagent.
(b) eaction of Aldehydes other than 6ormaldehyde+eaction of aldehydes other thanformaldehyde "ith GrignardSs reagents$follo"ed by acid hydrolysis producessecondary alcohol.
2hen
6etone! are treated "ith grignadreagents follo"ed by acid hydrolysis$ tertiary alcohols areproduced.
agents like chromic mi#ture (0a=5r =/7=!/> or 4=5r =/7=!/>) they are o#idi,ed tocorresponding carbo#ylic acids.
2hen 6etone! are treated "ith strong o#idi,ing agents likechromic mi#ture (0a=5r =/7=!/> or 4=5r =/7=!/>) theyare o#idi,ed to t"o molecules of same or different carbo#ylicacids. 5arbon adPacent to carbonyl carbon haing lesshydrogen is preferably o#idi,ed.
2hen al$eh)$e! are treated "ith mild o#idi,ing agents like6elingSs soln$ *enedictSs soln$ TollenSs reagent etc they areo#idi,ed to corresponding carbo#ylic acids "hich further reactto produce their salts.
6ehling !oln+ It is a mi#ture of 5u!/>$ 0a/7 and Tartaric acid.*enedictSs !oln+ It is a mi#ture of 5u!/>$ 0a/7 and 5itric acid.
TollenSs eagent+ It is a mi#ture of Ag0/<$ 07>/7.4ehlingH! Soln and Bene$ictH! Soln o#idi,es aldehyde to!odium salt of carbo#ylic acid "hile its self reduces to reddishprecipitate of cuprous o#ide. This reaction can be used for identification of aldehydes as "ell as for sugars.
TollenH! #eagent (ammoniacal siler nitrate soln) o#idi,esaldehyde to Ammonium salt of carbo#ylic acid "hile its self reduces to metallic siler that deposits on the "alls of the test
tube and makes mirror.
This reaction
can beused for identification of aldehydes and is kno"n as Sil#er &irror est D
<. -ldol Condensation Reactions+
"l$eh)$e! and 6etone! possessing alpha (j) hydrogen onreaction "ith cold dilute alkali produce additions productkno"n as aldols. -bond of carbonyl group of one molecule isbroken up "hile j-hydrogen of other molecule detaches and
gets attached to the o#ygen of first molecule "hile rest of thepart adds to the carbonyl carbon.
e.g. (i) Acetaldehyde (Ethanal) has j-hydrogen so itundergoes aldol condensation.
e.g. (i) 6ormaldehyde (Methanal) has no j-hydrogen so itundergoes canni,,aroSs reaction "hen treated "ith alkali.
e.g. (ii)*en,aldehyde has no j-hydrogen
so it undergoes canni,,aroSs reaction "hen treated "ithalkali.
$entification of "l$eh)$e! an$ Ketone!+
6ollo"ing are fe" tests used for identifications ofaldehydes and ketones.
. ,enedict+s Solution Test +
*enedictSs !olution is a mi#ture of 5u!/>$ 0a/7 and 5itricacid. It is a blue colour solution. 2hen an aldehyde solution isadded to benedictSs solution and boiled a brick red colouredprecipitate of cuprous o#ide is formed.Ketone! do not gie this test.
This test is also used as clinical test for sugar. Glucose (asugar) is secreted in urine of diabetic patients. 'rine of thepatient is added to benedictSs solution and is boiled$precipitate of cuprous o#ide is produced. 5olour of precipitatedetermines uantity of sugar in urine. Barker is the colour of precipitate greater is the amount of sugar in the urine.
=. 0e
h
ling+s Solution Test +6ehling !olution is a mi#ture of 5u!/>$ 0a/7 and Tartaricacid. It is a blue colour solution. 2hen an aldehyde solution isadded to fehlingSs solution and boiled a brick red colouredprecipitate of cuprous o#ide is formed.
Ketone! do not gie this test.(eaction same as in aboe)
<. Sil%er 2irror Test or Tollen+s Reagent Test +
TollenSs eagent is a mi#ture of Ag0/<$ 07>/7. 2henan aldehyde solution is added to tollenSs reagent in a test tubeand the tube is "armed gently$ siler is produced. The siler thus produced is deposited along the inner side of test tubeand forms mirror.
2hen alkaline sodium nitroprusside solution is added drop"isely to a ketone$ blood red or orange red colouration isproduced.
"l$eh)$e! do not gie this test.!e! of 4oral$eh)$e:
. It is used as a general antiseptic.=. It is used for manufacturing plastic such as
bakelite.<. It is used for preparing dyes such as indigo$ para-
rosaniline etc.>. Its >Q aueous solution called 6ormalin is usedas an antiseptic$ a disinfectant$ a germicide$ afungicide and for presering biological specimens.
?. 6ormalin is also used for sterili,ing surgicalinstruments.
@. It is used for silering of mirrors.. It is used for preparing anti-polio accine.
C. 6ormaldehyde and lactose are used in throatlo,enges.
H. It is used in making 'rotropine urinary trackantiseptic.
. It is used to prepare cyclonite "hich is a po"erfule#plosie.
!e! of "cetal$eh)$e:
. It used for manufacturing of acetic acid$acetic anhydride$ ethanol etc.
=. It is used as an antiseptic inhalant in nasalinfection.
<. It is used in silering of mirror.>. It used for preparing $<-butadiene "hich isused in rubber.
?. It is used in making drugs and dyes.
!e! of "cetone:
. It is used as nail polish remoer.
=. It is used for storing acetylene.<. It is used for e#traction of essential oils.>. It is used as organic solent.?. It is used for preparing chloroform (an anesthetic)
and iodoform ( an antiseptic).@. It is used in artificial scent.. It is used in making cordite (smokless gun po"der)
and ple#iglass (unbreakable glass).
C. It used for making mono$ di and tri chloro acetones"hich are chemical "eapons "hich deactiateeyes temporarily.
2hen primary alcohols are treated "ith 5hromic mi#ture(4=5r =/7=!/>) the o#idi,e to their correspondingaldehydes "hich further o#idi,es to correspondingcarbo#ylic acids.
=. *y 7ydrolysis of Esters+
a. Acid 7ydrolysis+2hen esters are treated "ith dilute acid$ they are hydroly,edto gie carbo#ylic acid and alcohol.
2hen esters are boiled "ith concentrated alkali solution$ theyproduce salt of carbo#ylic acid "hich then on treating "ithdilute acid (75l) produce carbo#ylic acid
<. *y the reaction of Grignard eagents "ith 5/=+eaction of GrignardSs reagent "ith 5arbon dio#ide follo"edby acid hydrolysis produces carbo#ylic acid haing one morecarbon than grignard reagent.
>. 7ydrolysis of 0itriles+
5ompounds haing a cyanide group are called alkylnitriles or alkyl cyanides. The carbon-nitrogen triple bond of
alkyl nitriles can be hydroly,ed to a carbo#ylic acid inaueous acid medium.
Structure:
The structural feature of carbo#ylic group are most prominent
in formic acid. It is planer "ith 5-/ is shorter than other carbon and o#ygen bond. The bond length of carbonyl groupis =pm "hile the bond length of other carbon and o#ygenatom is <>pm. !imilarly the bond angles of 7-5K/ is =>$"hile 7-5-/ is $ and /-5K/ is =?. This suggests !&=hybridi,ation of carbon and carbon-o#ygen double bondsimilar to that of aldehyde and 4etones. !imilarly sp=hybridi,ation of hydro#yl o#ygen allo"s one of its unshared
electron pair to be delocali,ed by orbital oerlap "ith pisystem of carbonyl carbon.
"ci$it):
The carbo#ylic acids are acidic in nature as theydonate proton and forms salts "ith bases. The
carbo#ylate ions formed after loss of proton$ are sabledue to resonance.
If electron pulling groups (like 5l$ *r$ 6$ /7$ 50 etc)are attached "ith the carbo#ylate ion it "ill increase the acidstrength and if electron donating groups (like etc) areattached "ith the carbo#ylate ion it "ill decrease the acidstrength.
*eing acid$ they on reaction "ith alkalis produce salt and"ater
2ith bases haing carbonates or bicarbonates$ they besidesalt and "ater also produce carbon dio#ide.
&ropanoic acid (&4a K >.C)$ Ethanoic acid (&4aK >.@)$Methanoic acid (&4a K <.@C)5hloroacetic acid (&4aK .=H)$ Trichloroacetic acid (&4aK.@?).
(i) The first ten carbo#ylic acids are colourless liuids"ith disagreeable smell "hile higher members arecolourless odourless "a# like solids.
(ii) Aromatic acids are crystalline solids e.g. ben,oicacid.
(iii) The first four members are soluble in "ater due tohydrogen bonding. The solubility in "ater graduallydecreases "ith the increase in molecular mass.
(i) The boiling points of carbo#ylic acids are higher than
corresponding alcohols due to hydrogen bonding.() The melting points of carbo#ylic acids increaseirregularly "ith increase in molecular mass. Themelting points of carbo#ylic acids haing eennumber of
carbon atoms are higher than the precedingand follo"ing members haing odd number of
carbon atoms.
(i) Their boiling points increase regularly "ithincrease in molecular masses.(ii) They are "eak acids. Their acidic strength
decreases "ith increase in molecular mass.
• 6ree,ing point of anhydrous acetic acid is
@o5. !o at this temperature it is in solid
form. The ice like solid form of anhydrousacetic acid is called glacial acetic acid.
The carbo#ylic group is so named because it containscarbo#yl group and hydro#yl group. These t"o groupsinfluences each other to such an e#tent that reactiity of carbo#ylic acids resembles to both aldehyde 1 ketones andon the other hand "ith alcohols. 5arbo#ylic acid containscarbonyl group butlike aldehyde andketones they do
not undergoescondensationreactions$ because the carbonyl carbon is less positie thanaldehyde and ketones.
The &olar carbonyl group attracts the electrons a"ay from/7 bond and make it easier from the hydrogen atom toioni,es than in the case of /7 bond of alcohols. 7ence
carbo#ylic acid sho"s different chemical reactiity thanalcohols. !imilarly the flo" of electron form /7 to carbonylcarbon is reduced and decreases is partial positie charge soit also reduces the probability of attack of nucleophile.
Cheical Propertie!+
1D 4oration of "ci$ ali$e!, "c)l ali$e!#-CO-5:
2hen carbo#ylic acids are made to react "ith phosphorushalides or thionyl chloride$ corresponding acid halides areproduced. Acid 7alides are deriaties of 5arbo#ylic acids.
9D 4oration of E!ter!:5arbo#ylic acids on reaction "ith alcohols in presenceof strong acids (7=!/>)$ produce esters. Esters arederiaties of 5arbo#ylic acids.
Mechanism of the reaction+
!tep-I+ &rotonation of carbo#ylic acidIn this step a proton from acid catalyst is added to carbo#ylicacid.
!tep-II+Attack of AlcoholIn this step alcohol molecule offers its lone pair of electrons topositiely charged carbon of protonated acid and get attached"ith it.
!tep-III+ 7ydrogen ion transfer In this step a hydrogen ion transfers.
!tep-I%+ Elimination of "ater and protonIn this step a "ater molecule and a proton is
eliminated and thus ester is produced.
3D 4oration
of "ci$ "nh)$ri$e!:5arbo#ylic acids undergo dehydration "ithphosphorus pentao#ide to form acid anhydride. Acid
Anhydrides are deriaties of 5arbo#ylic acids.
"i$e!:They are less reactie deriaties of carbo#ylic acids. 7ere
the /7 is replaced by 07= group. They are also kno"n asacid amides. They are named by replacing D ic acid or Doicacid of corresponding acid by the "ord Damide.
Amides can be prepared by the reaction of ammonia "ithcarbo#ylic acid to from amides and ammonium salt.
6ormation of Acid Amides+5arbo#ylic acids are first conerted to acid halides or acid anhydrides "hich then on reaction "ith ammoniaproduces acid amide. Acid Amides are deriaties of 5arbo#ylic acids.
5arbo#ylic acids on reaction "ith lithium aluminum hydridereduce to corresponding alcohol.
0ecaro.)lation #eaction!:The remoal of 5arbon dio#ide from carbo#ylic acid is
kno"n as decarbo#ylation. This reaction takes place "hensalt of carbo#ylic acid is heated "ith soda lime ( dry mi#ture of caustic soda$ 0a/7 and uick lime 5a/) to form alkanes.
#eaction! of Caro.)lic "ci$ 0eri(ati(e!:
4rie$el I Craft! "c)lation #eaction:2hen ben,ene is treated "ith acyl halide in
presence of 6e*r < or Al5l< it gies substitution product i.e.
aromatic ketone.
Acylation of ben,ene gies mono substituted product.)$rol)!i! of "ci$ "nh)$ri$e:
Esters are commonly hydroly,ed "ith bases. This iscalled saponification reaction$ because this type of reaction isused to make soaps from fats. 2hen 0a is used "e get bar
soap$ "hen 4 (potassium) is used "e get liuid soap.
#e$uction of E!ter!:
Esters can be reduced to primary alcohols in the
presence of reducing agent (lithium aluminum hydride) inether "hich is used as solent.
#eaction of E!ter! /ith %rignar$ #eagent:
eaction of GrignardSs reagent "ith esters other than alkylformate follo"ed by acid hydrolysis produces tertiary alcohol.
The addition product is not stable thus it undergoesrearrangement and produce ketone.
The substances on "hich life depends are called life or biomolecules. They are built from carbon skeleton. Many of themare ery large molecules and are called natural polymers or biopolymers. They include carbohydrates$ lipids$ proteins$en,ymes and nucleic acids.
Caroh)$rate!:
They "ere gien the name carbohydrates as they "erebelieed to be hydrates of carbon e.g. glucose 5@7=/@ or 5@.@7=/$ sucrose 5=7==/ or 5=.7=/. Thuscarbohydrates can be represented by general or empiricalformula 5#(7=/)y. The carbohydrates are also called sugarsor saccharides.
*ut later on inestigations sho"ed that there are compounds"hich are hydrate of carbon but they are not carbohydratese.g. 6ormaldehyde 57=/$ actic acid 5<7@/<. !imilarly thereare compounds "hich carbohydrates but they are not hydrateof carbon e.g. Mannitol 5@7>/@. !o the "ord D5arbohydratehae lost its original meaning and no"-a-days carbohydratesare defined as poly-hydro#y aldehydes or poly-hydro#yketones.
5arbohydrates are mainly consists of carbon$ hydrogen ando#ygen in ratio of +=+$ but some time ratio is different as inMannitol. !ome hydrocarbons also contain nitrogen andsulphur. 5abohydrates proide > kcal energy per gram.They are mainly classified into three categories.
'i* Mono !acchari$e!:The carbohydrates "hich cannot be hydroly,ed to further
simpler substances are called monosaccharides. They further diided into+(a) Trioses+ They consists of < carbon atoms e.g.glyceraldehyde 5<7@/<.(b) Tetroses+ They consists of > carbon atoms e.g.erythrulose 5>7C/>.(c) &entoses+ They consists of ? carbon atoms e.g.ribose$ arabinose 5?7/?.
(d) 7e#oses+ They consists of @ carbon atoms e.g. glucose$fructose$ galactose and mannose 5@7=/@. 7e#oses are themost important class of monosacchrides.(e) 7eptoses+ They consists of carbon atoms e.g.sedoheptulose 57>/.
The carbohydrates "hich on hydrolyses gie =-monosaccharides units are called oligosaccharides. The one"hich consists of = monosaccharide units are calleddisaccharides e.g. Maltose$ actose$ !ucrose etc 5=7==/
and the one "hich consist of < monosaccharide units arecalled trisaccharides e.g. raffinose 5C7<=/@. 'pon hydrolysisthey either gie similar or different types of monosaccharides.
6or e#ample maltose yields the same kind of t"o glucoseunits upon hydrolysis.
2hile sucrose yield t"o different types of monosaccharides upon
hydrolysis.
%l)co!i$e! Lin6age or Bon$:It is the linkage or bond bet"een t"o rings in
an oligosaccharides or polysaccharidesduring the formation of ne" molecule. T"o
monosaccharides units combines together iao#ygen atom and "ater molecules iseliminated. !uch kind of linkage is called glycoside linkage or
bond. 6or e#ample maltose yields the samekind of t"o glucose units upon hydrolysis.
2hile sucrose yield t"o different types of monosaccharides upon
hydrolysis.
(ii)Pol)!acchari$e!: The carbohydrates "hich on hydrolyses gie manymonosaccharides units are called polysaccharides e.g.starch$ de#trin$ glycogen$ cellulose etc.(5@7/?)n n7=/ dil 7=!/>n 5@7=/@
!tarch GlucoseStarch:
It is the most important source in human diet. It ispresent in "heat$ rice mai,e$ potatoes and barley. It is apolymer of j-B-glucose. !tarch gies blue colouration "ithiodine.
Cellulose:It is the most abundant form of polysaccharides.
&lants produce billion tons of cellulose per year. 5otton isHHQ cellulose$ "oody parts of plants are more than ?Qcellulose. It is the building material of plants. It is polymer of -B-glucose.
Glycogen:Glucose changes to glycogen and is stored in lier. Itis also called animal starch.
4unction! of Caroh)$rate!:
The basic and important function of carbohydrates is the chief source of energy to perform ital daily actiities of life. That is"hy they are called as Dfuel of life. They o#idi,e to produceenergy.
5arbohydrates /#ygen------------------ 5arbon Bio#ide "ater energy (>.4 cal).
. Glucose is used as an immediate source of energy for sick and sportsmen. 'sed in the preparation of Pamand Pellies.
=. 6ructose is used as s"eeting agent in confectionaryand medicinal products like syrup. It is also used topreent the formation of yello"ish color in ice cream(sandiness). Most importantly used as an alternatieof table sugar for obese and diabetic patients.
<. !ucrose is used as food and important ingredient in Pam $ Pellies and other s"eet products. 'sed in thepreparation of sucrose octa octate for denaturing of alcohol and for making anhydrous adhesies.
>. !tarch is mainly used as food. 'sed for the productionof ethanol industrially. In paper industry starch is usedas stiffening agent$ "hile in te#tile and laundry alsoused for same purpose.
?. 5ellulose has no food alue but it proides bulkinessto our diet for the normal peristaltic motion of our intestine.
@. /ligosaccharides are inoled in the formation of secreted proteins like antibodies and blood clotting
factors.. The receptor on the cell membrane are comple#carbohydrates "ith certain proteins. These receptorsare responsible for molecular recognition.
C. !ome deriaties of carbohydrates like glycol$ heparinsulphate are inoled in the attachment of adhesionof neurons to one another during the deelopment of nerous system. 7eparin sulphate a linear
polysaccharides formed in all animal tissues$ hae animportant role in Al,heimerSs and &arkinsonSsdiseases.
#ole of (ariou! Caroh)$rate! in ealth an$ 0i!ea!e!
Bifferent kind of carbohydrates are inoled in health anddisease of liing beings. !ome of important functions arelisted as follo"+
. !ucrose+ it is disaccharides$ used as s"eeteningagent and as source of energy. *ut the use of sucroseis primarily responsible in tooth decay and obesity. Itdeposited the plaue "hich is sucrose on our teeth.
=. actose+ it is also disaccharides of glucose andgalactose$ also kno"n as milk sugar$ mainly found inthe milk of mammals. 7uman milk contains @.CQ "hileco" milk contains >.CQ lactose. actose is digestedby lactase en,ymes. Although milk is uniersal foodbut some of human being cannot digest milk due todeficiency of lactase en,yme this is called lactoseintolerance. General indications of this disease isabdominal bloating$ cramps$ flatulenceSs$ colic pain$
nausea$ "atery diahoerrah. !ymptom appears usually"ithin <-H minutes after the ingestion of milk. Toaoid such problem fermented milk products likeyogurt$ cheese should be consumed.
<. Glucose+ the most common and popular monosaccharides.
• 6ound in s"eet fruits like grapes "hich contains =-<Q glucose.
• 'sed for uick energy source.
• Important part of human blood. 0ormally human bloodcontains @?- mg of glucose per ml• The e#cess glucose is stored in lier in the form of
polymer kno"n as glycogen$ "hich upon hydrolysisgie back glucose at time of need.
• 7uman pancreas secretes a hormone kno"n asInsulin. 2hich helps in the metabolism of glucose toproduce energy.
• !ometime defects in metabolism of glucose occurs"hich leads to increase leel of glucose in bloodcauses a disease kno"n as diabetes mellitus.
• The conseuences of unchecked diabetes causeshardening of blood essels$ dysfunction of kidneys$diabetic coma "hich causes premature death.
Nutritional portance: 5arbohydrates are most important energy containing
nutrients for liing organisms. &lants contains stored carbohydrates called starch$
"hile animal carbohydrates are glycogen. *oth these polymers are broken do"n into the
simplest units kno"n as glucose. 'pon o#idation reaction glucose molecules liberates
energy in the form of AT& "hich is >. 4 cal per gramof carbohydrates used for the normal function of human body.
The term protein is deried from the Greek "ord DProteo!e"hich means of Prie iportanceD This name "as chosen byMulder in C<H for a group of nitrogen containing compoundsthat he belieed "ere fundamental constituents of protoplasm.In fact$ proteins are the building block units of the cellular$ sub-cellular and organic structures. 7ence$ they are the mostessential bio-molecules reuired for gro"th and maintenance of
life. In biochemical terms "e can define them as follo"s+&roteins are comple# nitrogenous polymericsubstances$ "hich being macro-molecular arecolloidal in nature$ and built up of amino acids
Poined together by amide (peptide) bonds.
The amino (07=) group of one amino acid and the
carbo#ylic (5//7) group of an other amino acid form the ioniclinkage (-5o-07-) "ith the elimination of "ater. This coalentlinkage is called the peptide linkage or bond. The resultingcompound called a peptide. The consists of ?Q5$ Q7$=<Q/$ @Q0 $ -<Q ! and Q &. &rotein on hydrolysisproduce amino acids.&rotein is maPor structural component of animal tissue ascellulose is that of plant cells. They hae ital role in life as life
"ithout protein is not possible.
&roteins$ carbohydrates and fats are three maPor classes of food stuff collectiely kno"n as DTriumirates$ but function of protein is more important as beside proiding energy (>.->.Ckcal per gram) it also furnish certain essential componentsof liing tissue of organism itself. They are carriers of itamins$ /= and 5/=. 6urthermore they also hae catalyticand signaling role.&roteins are ery complicated substances and erychangeable in composition.
The precise classification of proteins is not possible onchemical basis as their structure is more comple#. Accordingto a system recommended by American !ociety of *iological5hemists$ the proteins hae been diided into three maingroups$ "hich are further sub-classified into a number of sub-groups. This classification is based on the chemicalcomposition and solubility of proteins. The three maPor groupsare+
i. !imple &roteinsii. 5onPugated &roteins andiii. Beried &roteins
iD SMPLE P#OTENSThese are the proteins "hich on hydrolysis yield only
amino acids or their deriaties. They are further sub-diidedinto+
aD "luin!: They are soluble in "ater$ coagulated byheat and deficient in glycine. They occur in both plant andanimal kingdoms. E#amples are+
!erum albumin (in blood)/albumin (in eggs)$
actalbumin (in milk)$ andegumelin (in plants).
D %loulin: These are insoluble in "ater$ but soluble indilute salt solutions$ and are heat coagulable to a ariablee#tent. E#amples are+
!erum globulin (in blood)$
/oglobulin (in eggs)$actoglobulin (in milk) andegumin (in legumes)$%icilin (in legumes).
cD %loin!: These are rich in histidine. They combine "ithheme (an iron containing pigment) to form hemoglobin (7b).They occur only in animal as their blood component.
$D %lutelin!: They are insoluble in "ater and other neutralsolents$ but soluble in dilute acids and alkalies. They occur only in plants. E#amples are+
Glutelin (of "heat) and/ry,enin (of rice).
eD %lia$in! or Prolain!: They are also insoluble in"ater$ neutral solents and absolute alcohol$ etc$ but soluble in to CQ alcohol. As the name indicate$ prolamines containmuch proline$ but deficient in lysine. They are the plant proteinsgenerally found in seeds. 6or e#ample+
9ein (in corn seeds)7ordein (in barley seeds) and
Gliadin (in "heat seeds).fD i!tone!: They are soluble in "ater$ but insoluble indilute ammonia. They are readily soluble in dilute acids andalkalies$ and coagulated by heat. 7istones are strongly basic asthey are rich in arginine. In combination "ith deo#y-ribosenucleic acid (B0A)$ they form nucleoproteins or more correctlynucleohistones$ "hich occur in cell nuclei forming chromatinmaterial. E#amples are+ thymus histone in animals and glutenin
in plants (i.e. "heat).
gD Protaine!: They resemble histones$ but unlike themare soluble in ammonium hydro#ide. They are large polypeptideand yield basic amino acid on hydrolysis (particularly arginine).They are not coagulated by heat and can precipitate other proteins from solutions.
&rotamines are present in sperm cells. They arerelatiely of small si,e. E#amples are the salmine of salmon(fish) sperm$ and the protamines of other sperms.
hD Scleroprotin! or "luinoi$!: These are the leastsoluble proteins. They are insoluble in "ater$ salt solutions$dilute acid and alkalies$ and in alcohol. They are of animalorigin and do not occur in plants. E#amples are+
Elastins of elastic tissues (tendons$ arteries)$collagen of bones and cartilage$ keratins foundin nails$ hairs$ "ool$ hoofs and horns etc3 andfibroin of silk.
iiD CONQ%"TE0 P#OTENS
These are the proteins "hich are formed by thecombination or conPugation of simple proteins "ith non-proteinsubstances called pro!thetic group!D The conPugatedproteins$ sometimes also kno"n as compound proteins$ are of great biological significance. They are part of the en,ymesystems in most biochemical reactions that are indispensablefor life. !ome hormones are also conPugated proteins and
regulate the metabolic processes.aD Nucleoprotein!: 0ucleic acids conPugate or attached tocertain basic proteins (histones and protamines) and formnucleoproteins.D %l)coprotin!: 5arbohydrates unite "ith simpleproteins$ the resulting compound is kno"n as gl)coprotein!D cD Mucoprotin! or Mucoi$!: These are the combination
of mucopolysaccharieds "ith simple proteins. They generallycontain more than >Q he#osamine. E#amples are seeralgonadotropic hormones$ such as interstitial cell stimulatinghormone (I5!7) and follicle stimulating hormone (6!7).
$D Liporotein!: ipids such as lecithin$ cephalin$cholesterol and fatty acid combine "ith simple proteins andyield lipoproteins. They occur in blood plasma$ nerous tissue$
egg yolk$ milk and cell membranes.eD Pho!phoprotein!: These are the phosphorouscontaining proteins. &hosphoric acid or other substancescontaining phosphorus (e.g. lecithin$ cephalin$ etc) combine
"ith simple proteins to form phosphoprotein. E#amples are thecaseinogen found in milk and itellin found in egg yolk.
fD Chrooprotein!: These are the compounds of proteins "ith coloured substance$ "hich sere as prostheticgroup. &igment such as heme combine "ith globins to form thered coloured hemoglobin (7b).
gD Metalloprotein!: !ome metals or metallic compounds
combine "ith simple proteins and yield metalloproteins.5ommon metals in these proteins are iron$ cobalt$ ,inc$ ferric$magnesium and manganese.
iiiD 0E#2E0 P#OTENS
These are the deriaties of higher proteins producedby the action of en,ymes$ chemical reagents$ and arious
physical forces. They may be (a) primary or (b) secondaryderied proteins.
'a* Priar) $eri(e$ protein!+ They are formed by processes$"hich cause only slight changes in the protein molecule. Thereis no or little hydrolytic cleaage of the peptide bonds. Theseinclude four kinds of proteins+
Protean!: These are the insoluble deriaties formed by theaction of "ater$ dilute acids or alkalies and en,ymes on simpleand conPugated proteins.Metaprotein!: These are produced by the action of acids andalkalies. 6or e#ample$ the acid albuminates$ and the alkalialbuminates.
Coagulate$ Protein!: These are formed by the action of heat$
'%-light$ 8-rays and alcohol. They are actually denaturedproteins. E#amples of such proteins are cooked egg albumin$cooked meat proteins$ and alcohol precipitated proteins.
'* Secon$ar) 0eri(e$ Protein!: These are the productsof the progressie hydrolytic cleaage or breakage of thepeptide bonds of simple proteins. They are "ater soluble andnot coagulated by heat.
GD@ ST#CT#E O4 P#OTENS
&rotein functions are directly related to its structure.The biological actiity and all the properties of a specific
protein depend on the structure of the molecule as it e#ists inits natural surroundings$ that is$ in the body tissues or fluids.&roteins range in comple#ity from a small simple polypeptideto a more comple# globular protein. The arious leels ofcomple#ity or organi,ation of proteins$ "hich constitute theircomplete functional structure are primary$ secondary$ tertiary$and or uaternary.
'i*D Priar) Structure:
It refers to the numbers and order of amino acids in apolypeptide chain. Asstated earlier$ aminoacids Poined together by coalent peptide
bonds$ and constitutea polypeptide. !o thestructure of a specificpolypeptide "ill bedifferent from other polypeptide by the number and seuence of amino acids. Thisis kno"n as the primary structure of proteins. It should alsoindicate "hether the peptide chain is open$ cyclic or branched.
The number of amino acids in a peptide molecule ariesfrom a fe" to seeral hundred or more. The substitution of asingle amino acid by another in a peptide chain may result in adrastic change in its properties and biological functions.
*oine (beef) insulin "as the first protein$ "hoseprimary structure (amino acid seuence) "as established inH??. This "as done at 5ambridge 'niersity in England by6rederick !anger$ "ho "as a"arded the 5hemistry 0oble &ri,ein H?C for the said "ork.
Insulin is a small protein hormone produced by the -cells of pancreas "hich has a physiological influence on glucose
The regular arrangement or coiling of segments (amino acidchains) of a polypeptide iskno"n as the secondarystructure. /ne sucharrangement$ called theα
-heli#$ occurs "hen theamino acids form a coil or spiral. The coil consists of loops of amino acids held together by hydrogen bonds (bet"een the -7of the -07= of one amino acid and the / of the 5 K / of theacid part of another amino acid. Each turn of the heli# containsan aerage <.@ amino acids !uch a structure is both fle#ibleand elastic.
The α-heli# protein structure "as discoered by inus&auling of the 5alifornia Institute of Technology$ "ho is t"o time"inner of the 0oble &ri,e for his "ork on protein structure.
iiiD Tertiar) Structure:
It refers to the specificfolding and bending of the coilsinto specific layers or fibers. Thecompact and rigid structure thusformed$ called the tertiarystructure of the polypeptide$ isresponsible for its biologicalactiity. The tertiary structure ismaintained and stabili,ed by four different types of interactions or bonds. These are+
a. 7ydrogen bonds formed bet"een differentsegments of the coil$
b. Bisulfide bonds formed by cysteine groups indifferent parts of the coil$
c. Ionic bonds (salt bridges) formed bet"eenpositiely and negatiely charged groups "ithinthe polypeptide molecule.
d. 7ydrophobic bonds (%ander 2aals forces)bet"een non-polar side-chains$ "hich are insidethe folded structure$ so that to be in closecontact "ith one another$ and in minimal contact
"ith the aueous solution surrounding thepolypeptide.
The polypeptide "ith a stable shape as its tertiary structure$constitute the monomeric protein unit$ called protomer.
i(D Ruaternar) Structure:
2hen more than onepolypeptide units (protomers) Poined together by non-coalent bonds$ the resultingoligomeric protein structure iscalled the uaternary structure.In other "ords$ the associationand fit of one protomer into an
other in an oligomeric proteinconstitute the uaternarystructure. Each polypeptideunit or protomer "ithin anoligomeric protein is already coiled and folded into itssecondaryand tertiary structures. These fully arranged and folded unitsare then associated "ith one an other through attractie "eak
interactions$ "hich may be hydrogen bonding$ salt bridges$ andespecially hydrophobic interactions.
An e#ample of a protein "ith a uaternary structure ishemoglobin$ the o#ygen carrier "ithin the red blood cells. Itconsists of t"o identical alpha monomeric units$ and t"o
identical beta monomeric units. Each unit enfolds a heme (ironcontaining) group. The alpha and beta units fit together to yieldthe uaternary structure of hemoglobin. It is maintained by non-coalent interactions$ particularly by hydrophobic interactionamong the four sub-units. 5ommon e#amples of globular proteins are the natie albumins$ globulins$ insulin$ hemoglobin$myoglobin$ pepsin$ trypsin and ,ein. An important e#ample of fibrous protein is collagen of connectie tissue and myosinfibrin. &erut, and 4endre" "ho established the tertiary
structure of myoglobin$ a protein related to hemoglobin alsoreceied 0oble &ri,e in H@=.
MPO#T"NCE:
&roteins are the basic life components. More than t"othousands different kinds of proteins are "idely distributed innature. These proteins are ital cell constituents$ "hich make
up its structure and regulate its functions. As part of thechromosomal structure$ proteins sere as the hereditarymaterials.
• &roteins in the form of en,ymes catalyse all biochemicalreactions. In plants$ en,yme proteins form comple#es"ith chloroplast pigments (chlorophylls andcarotenoids). The coloured protein or chromoprotiencomple#es so formed are inoled in the capture of
solar energy$ and in the 5/= fi#ation duringphotosynthesis
• &roteins in the form of haemoglobin act as o#ygencarriers and thus transfer o#ygen to the remote cornersof the body. As cytochromes$ proteins are inoled inthe electron transport system$ "hich regulate the energyproduction. !ome hormones (e.g. insulin) are proteins..
• !ome proteins act as antibodies$ "hich protect the bodyagainst infectious diseases$ "hile others are part of thebuffer system of the cell and e#tracellular body. The
proteins present in the blood plasma e#ert an osmoticpressure of =? to < mm 7g.
• The presence of proteins in the muscles and tendonsfacilitate the moement of the body. !ome proteins asconstituent of skin and hairs proide an outer coeringof the body. &roteins in blood plasma take part in theblood coagulation or clotting process$ "hich is importantto preent e#cessie bleeding of "ounds and inPuries.
• 6or the aboe reasons$ proteins are the essential part of our daily diet and sere as a source of energy. Eachone gram of protein furnishes >. kilocalories "heno#idi,ed in the body.
• Beficiency of protein in the diet results negatie nitrogenbalance and a fall in plasma protein and hemoglobin(7b) leels. This adersely affects the gro"th and
deelopment$ and normal functions of the body. 7ence$protein malnutrition in infant caused ara!u!disease$ and in children of to < years result in diseaseconditions$ called 6/a!hior6orD These diseases arecharacteri,ed by diarrhea$ infections$ s"ollen bellydiscoloration of skin and hairs$ mental apathy$ lo"intake of food and stunted gro"th. In adults and elderly$lo" intake of protein caused muscle degeneration andbody "eakness.
• In order to understand ho" proteins play so many italroles as mentioned aboe$ "e must study their structures and properties$ and relate them to their biological functions. et us first define and classifyproteins$ and then touch their other biochemical
aspects.En+)e!+The "ord en,yme is Greek in origin. DEn means in andD,yme means yeast$ so en,yme means in yeast.
!ante Arrhenius suggested that substrate combine "ithen,yme catalyst and forms en,yme-catalyst comple# of lo"er energy$ "hich then changes to products.
! E J E-! J & E Actual mechanism is yet not completely understood. 7o"eer it can be better e#plained by lock 1 key model. The substratefits into actie site of en,yme as key fits into lock. As a resulten,yme-substrate comple# is formed$ "hich then dissociates
and products are produced "hile en,yme is regenerated andready for ne#t molecule of substrate.
The functionalgroups "hich are essential for the formation of en,yme-
substrate comple# are present on specific site of en,ymemolecule kno"n as actie site. 2hile the site "hich is notactie is called allosteric site. Actie site is usually a cleft andis complementary to the structure of substrate.
It may be defined as soluble organic catalysts$ "hich arecolloidal and protein in nature and are produced by the liingorganisms. In other "ords$ en,ymes are protein catalysts$
"hich regulate and accelerate the rate of specific chemicalreaction both "ithin and "ithout the liing cells that producedthem. All en,ymes in their inactie state are called Pro-en+)e! or +)ogen!. The substance on "hich an en,ymeact is called its !u!trate.
En,ymes may be simple or conPugated proteins. In conPugateden,ymes a non-protein segment (moleculeion) is attached "itha specific protein. The protein part of the en,yme is called apo-en+)e$ "hile the non-protein component is often referred toas co-factor. This co-factor if Poined loosely to the protein isusually kno"n as co-en+)e. The term pro!thetic group is
used for a co-factor bound ery tightly by coalent linkages tothe apo-en,yme.
The complete en,yme "ith catalytic actiity is kno"n as holo-en+)e. In case of conPugated protein$ the holo-en,ymeconsists of the apo-en,yme co-factor (co-en,yme or prosthetic group). An en,yme "hich has the same catalyticactiity but different molecular structure is called i!o+)e.
4"CTO#S "44ECTN% ENFME "CT2TF
%ariation in en,yme actiity is important for theregulation and control of metabolic processes. In healthy bodyen,yme actiity is turned upN and do"nN as needed. There are"ays in "hich en,yme actiity can be increased or decreasedby e#ternal agents$ such as drugs and poisons. 5hanges inen,yme actiity are also caused in diseased or pathological
conditions. The important factors "hich affect en,yme actiityor the rate of en,ymatic reactions are briefly discussed asfollo"s+
aD En+)e-!u!trate contact
In order to proceed an en,ymatic reaction$ the formationof en,yme-substrate comple# is essential. 6or this purpose the
en,yme must be in good contact and "ell mi#ed "ith thesubstrate. !uch comple# mi#ture "ill be more effectie tocomplete the reaction. If the substrate is soluble$ the contactcan be established easily. En,yme-substrate contact alsodepends on the number of actie sites and the structure of boththe en,yme and substrate. 6or an effectie contact$ it is alsoimportant that both the en,yme and substrate must be presentin proper concentrations.
D Concentration of En+)e
All en,ymatic reactions are of the first order "hichindicate that the rate of reaction is directly proportional to the
concentration of en,yme. This is true "hen all other factors$such as concentration of substrate$ p7 and temperature arekept constant. In such cases "hen en,yme concentration isplotted ersus reaction rate$ a straight line "ill be obtained.
CD Concentration of !u!trate
The rate of en,ymatic reactions increases "ith an
increase in substrate concentration to certain limit. 2hen thislimit is e#ceeded$ no further increase in rate of reaction isobsered. This means that the reaction is of the first order tocertain e#tent of the substrate concentration$ but it become the,ero order reaction "ith further increase in substrateconcentration.
Effect of en,yme concentration on reaction rate "ith constantsubstrate concentration.
elationship of substrate conc. "ith en,yme actiity. (%mKma#imum elocity$ 4m K Michaelis-Menten 5onstant) The
straight cure indicates the first order reaction and the flatportion sho"s the ,ero order reaction.
The concentration of the substrate at "hich the elocity of thereaction is half of ma#imum elocity is called Michaeli!-Menten Con!tant$ denoted by K. This relationship of thesubstrate concentration "ith en,yme actiity .
$D Concentration of pro$uct!
The concentration of the end product of an en,yme-catalysed reaction often affects the rate of reaction. !ince allen,ymatic reactions are reersible$ the product must beremoed. /ther"ise$ it "ill rebind "ith the en,yme and the ne#tsubstrate molecule "ill hae no access to the en,yme. Thiscondition$ also kno"n as negati(e fee$ac6$ reduces theen,yme actiity. Moreoer$ e#cess accumulation of endproducts may affect p7 of the reaction enironment and thuscause a drastic change in en,yme action.
The en,yme actiity increases "ith a rise in temperatureupto to ?°5. An increase in temperature increases the number of effectie collisions bet"een en,yme and substrate to formthe actiated comple#$ and thus accelerate the reaction elocity.7o"eer$ in contrast to an ordinary chemical reaction$ the rateof en,ymatic reactions ceases at much higher temperature.This is because en,ymes being protein in nature are denatured
and become inactie at temperature aboe ?°5. Mosten,ymes are irreersibly destroyed bet"een and C°5.
Most en,ymes are actie in the temperature rangebet"een ° to ?°5. The temperature at "hich an en,ymeactiity is ma#imum$ is kno"n as its optiu teperature.This temperature of en,ymes "orking in the body of mammalsis about <° to >°5. !ome phyto-en,ymes (e.g. plant urease)act best at temperature around @°5. The effect of temperatureon en,yme actiity is sho"n in 6igure-.>.
En,ymes are ery sensitie to the reaction of their enironment. 5hanges in the hydrogen ion concentration "illgreatly affect their actiity. This is because all en,ymes areproteins or contain protein. A small change in p7 may influencethe ionic character of the amino and carbo#ylic acid groups onthe protein$ and thus affect the catalytic (actie) site andconformation (shape) of an en,yme. In addition to the purely
ionic effects$ lo" or high p7 can cause considerabledenaturation of protein$ and thus inhibit en,yme actiity.
As p7 affects the apo-en,yme$ co-en,yme andsubstrate$ it must influence the combination of en,yme andsubstrate to form an effectie comple# and thus regulateen,yme actiity. Each en,yme has an optimum p7 at "hichits actiity is ma#imum. This p7 aries from about =. for
pepsin to about C. in case of trypsin. The optimum p7 of thesame en,yme also aries depending on the nature of thesubstrate. The effect of p7 on the elocity of the en,yme-catalysed reaction can best be sho"n by a bell-shaped cure.The plateau indicates the optimal p7.
En,yme /ptimum p7&epsin .>!ucrase or Inertase @.=
&ancreatic amylase .Trypsin C.gD Effect of light
En,yme actiity is also affected by light. 'ltraiolet lightdestroys or modifies the action of en,ymes. The rate of destruction is independent of the temperature$ but affected byp7 etc. &urified en,ymes are more easily destroyed by the
ultraiolet rays than impure en,ymes. The ultraiolet lightprobably affect the protein conformation of en,yme and thusreduces their catalytic actiity. 'rease is inactiated byultraiolet rays irreersibly.
As stated earlier$ many ions and molecules hae theability to actiate or inhibit certain en,ymes$ and thus enhanceor reduce their catalytic actiity. Actiators act as inducers or co-factor of the en,yme system. Metal ions (e.g. (6e$ 9n$ 5u$ 5o$Mg and Mn) are actiators of a number of en,ymes. Theen,yme either contains these ions in their molecular structureor need them for actiation. !ome organic molecules act as
inducer of catalytic actiity by modifying their structure.&roteolytic ,ymogens are actiated by splitting a peptide bond$"hich is accomplished by actiators. In certain instances anen,yme act as an actiator of other en,yme.
n$u!trial "pplication of En+)e!:
En,ymes are used in the chemical industry and other industries
"here e#tremely specific catalyst are reuired. 'seful en,ymesare obtained from plants$ animals$ microorganisms$ fungi etc.some of the useful applications of en,ymes in industry+
. *iological Betergents+6or "ashing most of the en,ymes comes from bacteria adoptedto lie in hot springs. The en,ymes used for presoak conditionand direct liuid applications helping remoal of protein and
starch stains. They are also able to digest fat$ oil and greasestains.
=. 6ruit$ Luice &roduction+Buring manufacturing of fruit Puices. 6ruit cells hae beenbroken do"n before e#traction of Puice. &lant cell "all is built of cellulose fibers$ "hich are held together by pectinSs andhemicellulose and are e#tremely tough. The fruit are crushed
and en,ymes are added. This "ill break do"n the cell "all andliuid (Puice) is released.
In biofuel industry$ cellulase are used to breakdo"n celluloseinto sugar "hich can be further fermented to produce ethanolby the action of arious en,ymes.
Then another en,yme is secreted kno"n as maltase orinertase "hich further hydroly,e maltose into glucose.
Then a third en,yme is secreted kno"n as ,ymase "hichchanges glucose into ethanol and carbon dio#ide.
>. 7igh 6ructose !ugar+ A s"eetener that is "idely used in food and drinks is highfructose corn syrup. It is prepared from starch in corn fruit.Grains are milled to starch slurry and en,yme amylase is
added . finally the syrup is passed do"n to column of immobili,ed glucose isomerase en,ymes "hich conertsmuch of glucose into fructose.
?. &aper Industry+In paper industry en,ymes like amylase$ #ylanases$ cellulaseand ligninase are used. Amylase used to break starch intolo"er iscosity$ si,ing and coating of paper. !ylanases
produce bleach reuired for decolori,ing. 5ellulase smoothenfibers $ enhance "ater drainage soften the paper.
Lipi$!0aturally occurring heterogeneous group of organiccompounds "hich are insoluble in "ater and soluble inorganic solents like ether$ chloroform$ alcohol$ ben,ene andacetone$ are called lipids. 5hemically they are either esters of
fatty acids or substances "hich are capable of forming esters.They are found in animals and plants.They are simple or comple# lipids. The simple lipids areesters of fatty acids. !imple esters on hydrolysis produce fattyacids and alcohols. They include fats$ oil and "a#es.
6ats are saturated esters "hile oils are unsaturated esters.
Iodine number is used to determine the e#tent of unsaturation in a fat or oil. It is defined as the number of grams of iodine "hich "ill add to grams of fat or oil tomake it unsaturated. 7igher is the iodine number more is the
unsaturation.
5omple# esters or compound esters on hydrolysis produceother substances in addition to fatty acids and alcohols. Theyinclude phospholipids$ glycolipids$ sulfolipids$ lipoproteins$steroids including cholesterol.
ipids beside proiding energy they do other Pobs also e.g.
they proide insulation for ital organs$ protecting them fromelectric shock and maintain optimum body temperature. Theycontain fat soluble itamins and essential fatty acids.
CL"SS4C"TON
ipids generally contain fie elements+ carbon$hydrogen$ o#ygen$ and (less freuently) nitrogen andphosphorus. These elements form seeral types of lipids "ithdierse structures. !ince many lipids hae ester linkages$ "hichare susceptible to saponification (formation of soap)$ a commonreaction of esters. !ome comple# lipids are non-ester andhence non-saponifiable. Therefore$ "e can classify so many
lipid compounds into t"o maPor categories+ (i) saponifiable lipids(esters)$ and (ii) non-saponifiable lipids.
iD Saponifiale Lipi$!:
They are those lipids$ "hich react "ith strong alkalies(e.g. 0a/7$ 4/7) and yield salts of fatty acid (soap)$ alcohol$andor other components. They are further sub-diided into+
aD Siple Lipi$!: 2hich upon saponification yield onlyalcohols and salts of carbo#ylic acids (soap). Theseinclude fatsoils and "a#es. /n hydrolysis they yieldfatty acids and alcohols.
D Copoun$ Lipi$!: 2hich upon saponification yieldother compounds besides the aboe mentioned ones..They may be+
Pho!pholipi$!: 2hich contain phosphoric acid and asa chemical moiety. These include+ lecithins$ cephallins$phosphoinositides$ phosphatidic acids$ plasmalogens$and sphingomyelins.
%l)colipi$!: 2hich contain carbohydrate and anitrogen compound. They are also called cerebrosides
because they are found in the cerebrum of the brain.
Lipo-protein!: 2hich contain proteins. In order tosolubili,e simple lipids$ "hich are hydrophobic$ they arecomple#ed "ith proteins that are hydrophilic. !omelipid-protein comple#es formed larger structures calledchylomicrons.
It is the lipid fraction$ "hich remain after saponificationand can be separated by ether. The important un-saponifiablelipids are (a) prostaglandins (hormone-like substances)$ (b)steroids (se# hormones and other sterols and the fat solubleitamins (e.g. itamin-B) and (c) carotenoids (carotenes and#anthophylls $ that are plant pigments).
It is note-"orthy that lipids$ such as fatty acids$ glyceroland other alcohols$ etc are also called $eri(e$ lipi$!$ becausethey are deriaties of simple and compound lipids. 6atty acidsare the most important deried lipids found in nature. !ince theyare the basic essential components of most lipids$ they desereour first attention in order to understand the structure andproperties of other lipids. 2e therefore$ discuss fatty acids first$and shall then deal "ith other important lipids.
"5ES - Siple Lipi$!
2a#es are the esters of the fatty acids "ith long chain
monohydric alcohols. Generally$ the acids and alcoholsconstituting "a#es contain unbranched carbon chains "ith an
een number (= to <@) of carbon atoms. 6or e#ample$*ees"a# consists largely of palmitic acid (5?7<5//7) andmyricyl alcohol (5<7@/7). It is chemically kno"n as myricylpalmitate (5?7<5//5<7@). The naturally occurring
substances commonly called "a#es contain not only true"a#es$ but also mi#ture of other hydrophobic compounds such
• &ure fats and oils are generally tasteless and adourless$• "hite or yello" solids or liuids at room temperature.• They are insoluble in "ater$ but soluble in organic
solents$ like acetone$ ben,ene and ether.• *oth fats and oils are lighter than "ater and hae a
greasy feeling.• They form temporary emulsion "hen shaken "ith "ater.
The emulsion may be made permanent by the additionof an emulsifying agent$ such as soap.
• 6ats and oils must be emulsified by bile in the bodybefore they can be digested.
• 6ats are also non-dialysable$ that is they cannot passthrough a membrane.
i(D Cheical #eaction!
6ats and oils e#hibit the usual reactions of ordinaryesters. Triglycerides containing unsaturated fatty acids also giethe addition and o#idation reactions characteristic of alkene(!traight- chain compounds "ith double bonds). !omeimportant reactions$ of fats and oils are+
'a* )$rol)!i!
6ats and oils are easily hydrolysed in the presence of mineral acids$ alkalies or en,ymes$ called lipases. Thehydrolytic products are fatty acids and glycerol. 2hen tripalmitinis hydrolysed$ it forms three molecules of palmitic acid andglycerol.
This reaction caused by lipases$ takes place in the digestietracts of animals and human beings. The fatty acids soproduced play an important role in metabolic processes.
'* Saponification
Alkaline hydrolysis of fats and oils yields glycerol andalkali-metal salts of fatty acids. The reaction is calledsaponification because the alkali metal salts obtained are used
as soaps.
The sodium soap is the bar-soap. 2hen the saponifying agent
is 4/7$ potassium soap is produced$ "hich is soft and used asliuid soap. %arious substances may be added to soaps to giethem pleasant colour and odour.
Iodine alue+ 0umber of G of Iodine obsered by g of 6atoils!aponificatoin alue+ 0umber of mg of 4/7 reuired tosaponify g of fatoils
'c* )$rogenation 'ar$ening of oil!*
6ats and oils are similar compounds e#cept that oils aremore unsaturated$ that is$ they contain double bonds. Thesedouble bonds may be changed to single bonds upon theaddition of hydrogen. %egetable oils may be conerted to fat bythe addition of hydrogen in the presence of a catalyst (usually
nickel$ 0i). This process is called h)$rogenation or thehar$ening of oil!D
The hydrogenation of oils is used for the production of egetable ghee. In actual practice$ egetable oils are notcompletely hydrogenated. Enough hydrogen is added to
produce a solid at room temperature. If the oils "ere completelyhydrogenated$ the solid fat "ould be brittle and unsuitable for cooking purposes. 6inally$ it is mi#ed "ith flaouring agent and
synthetic itamins A and B. The product obtained resemblesghee in appearance$ and therefore$ it is marketed as (egetale
ghee or 0al$a ghee$ also called Bana!pati gheeD
$* )$rogenal)!i!: '#e$uction to "lcohol*
2hen e#cess of hydrogen at high pressure andtemperature is passed through a fat or oil$ in the presence of
copper chromite$ glycerol and a higher alcohol is produced+
This
reaction "hich cleaes the fat by hydrogenation is termedhydrogenolysis.
The uantity of halogen added (or absorbed) indicates
the degree of unsaturation of fats and oils. This is usually
measured in terms of iodine alue. It is defined as the number of gram of iodine absorbed by grams of oil to completely
saturate it. The greater the iodine alue$ the greater is thedegree of unsaturation. The iodine alue of some importantcommercial fats and oils .
'f* #anci$it)
6ats and oils deelop an unpleasant odour and taste"hen e#pose to air$ light and heat. This is due to the hydrolysisandor o#idation of the triglycerides$ "hich produce badsmelling and off flaour olatile acids$ aldehydes and ketones.This process is kno"n as ranci$it) or ranci$ification. The
product is usually referred to as the rancid fatoil.
2hen butter is kept at room temperature$ hydrolysis takesplace bet"een the fats and the "ater present in the butter. Theproducts of this hydrolysis are fatty acids and glycerol. /ne of the fatty acids produced$ butyric acid$ has the disagreeable
odour that causes one to say that the butter is rancid. This iskno"n as h)$rol)tic ranci$it)D
ipids sere as our food. They proide more energythan carbohydrates and proteins. The o#idation of each gram of fat supplies about H.< 4cal$ "hereas that of carbohydrate andprotein proides only >. 4cal. 2e store lipids in our body as anenergy reseres in the farm of adipose tissues.
In addition to their function as a concentrated source of energy$ lipids are the structural units of membranes$ Thus lipids
(i.e. phospholipids and sterols) create boundaries bet"eencells$ and sub-cellular organelles$ such as nucleolus$mitochondria$ chloroplasts$ etc. 2ithout such boundaries thestructure and function of the cell is not possible. 7ence$ lipidsare ital bio-molecules$ "hich make-up the maPor part of themembranes of each of the trillion cells in our bodies.
ipids also play an important role in the body transport$
metabolic and nerous systems. They are carriers of the non-polar (hydrophobic K "ater repelling) compounds$ such as thefat-soluble itamins (e.g. A$ B.E and 4). They sere aslubricants in the alimentary canal and in other sites of the body.ipids degradation products are the starting material for thebiosynthesis of other compounds inole in the body buildingand other processes. !ome hormones are lipids in nature. Theysere as Ncheical e!!enger!N and regulate the metabolic
processes of the body. 5ertain lipids (e.g. cerebrosides) areconstituents of brain$ "hich regulate the nerous system.
!ome simple lipids$ such as fat is stored in the form of adipose tissue and sere as a protector for the ital organs.That is$ fats surround the ital organs to keep them in place andalso act as shock absorbers. 6ats in the outer layers of thebody act as heat insulators$ helping to keep the body "arm in
In C$ scientists found a substance 0uceinstoffS in nucleusof cell "hich "as then named as nucleic acid. 0ucleic acids
are found in eery liing cell. They are comple#macromolecules$ as might be e#pected from the role they playas the information and control centers of the cells.
A nucleic acid is a molecular tape that is coded "ithdirections for proper construction of en,ymes and other
proteins - "hich$ in turn$ operate all the other structures andfunctions of the organism. It is no" kno"n that eachchromosome is a single nucleic acid molecule "ith a protein
sheath. *y means of chromosomes in the nucleus of a fertili,ed
oum$ parents donate to offsprings a complete set of information for the indiidualNs biological e#istence. 0ucleic acids are diided into t"o types B0A and 0A.0ucleic acids are responsible for reproducing$ storing andtransmitting genetic information.
B0A (deo#yribonucleic acid) is found in nucleus of cell inassociation "ith chromosomal material. Genetic informationare coded along the length of polymeric molecule$ B0A. Thusit is chemical basis of heredity and is fundamental unit of genetic information. B0A has double stranded structure "hich"as pointed by Lames 2aston and 6rancis 5rick in H?<.Bouble stranded structure uses a process kno"n asreplication. eplication is the process "hich proides a
mechanism for duplicating genetic information.0A (ribonucleic acid) is found in the cytoplasm of cell andalso smaller amounts are present in the nucleus. Genescontrol the synthesis of arious types of 0A$ most of "hichare inoled in the synthesis of proteins.
There are t"o main types of nucleic acids$ deo#yribosenucleic acid B0A$ and ribose nucleic acid 0A. B0A isprimarily responsible for the transfer of genetic information$
"hereas 0A is primarily concerned "ith the synthesis of
protein. The distinctie features of their coalent structures(primary structure) are as follo"s+
i. In 0A eery pentose residue is ribose$ and in B0Aeery pentose is deo#y-ribose. The prefi# $eo.) means/ithout o.)gen. Beo#y-ribose contains one less
o#ygen than does ribose
ii. The nitrogen bases (heterocycles) attached to thepolymer skeleton of B0A are all selected from a set offour possibilities+ A$ G$ 5 or T. The set of four possiblebases used for the construction of 0A are A$ G$ 5 or '.0ote that three of the bases are the same in the B0A set
2t.much higher than0A (may be up millions or more amu)
much smaller thanB0A (=?$ toone million amu)
. &entosesugar
deo#y-ribose ibose
i. 0itrogenbases(heterocycles)
contains thyminebesides other threebases
contains uracilinstead of thyminealong"ith otherthree bases
ii. ole real genetic material(carrier of heredity)
direct proteinsynthesis in thecell
iii Types only one typeduplicate or replicateitself
three types+ m-0A$ t-0A and r-0A.
ST#CT#E O4 0N"
B0A has the kind of secondary structure as sho"n in6igure. T"o molecular chains of B0A are aligned antiparallel
(that is$ side-by-side$ but oriented in opposite direction) and areheld together by hydrogen - bonds bet"een their bases.
Although the short segment of double stranded B0A
portrayed in (a) of appears to be 6lat$ 2atson and 5rickproposed that the t"o B0A strands actually "ound aroundeach other forming a $oule heli. as pictured schematically in
(b) 6igure H.>. The molecular "eight of the double heli# B0A
molecule may be upto millions or more amu.
Bouble helical structure of B0A.
ST#CT#E "N0 TFPES O4 #N"
0A differ from the B0A double heli# in three respects+(i) the sugar unit is ribose instead of deo#yribose$ (ii) the
thiamine in B0A is replaced by uracil in 0A$ and (iii) 0Aconsists not of a double heli# but a single strand or chain of nucleic acid monomer$ forming a chain considerably shorter
than B0A. 0A molecules hae a molecular "eight from
/f the t"o types of nucleic acids$ in plants and animals
B0A is the true genetic material$ the master file of information.Each chromosome is actually one immense double-strand B0Amolecule "ith a protein coating. 7umans hae forty-si#
chromosomes per cell$ and other mammals hae thirty to forty
four.
Each of the parents contributes half of the number of chromosomes. ess comple# organisms reuire lessinformation storage3 peas hae fourteen chromosomes and
bacteria hae one. *ecause of the incredible amount of
information that must be stored$ these molecular tapes aresurely the polymer chains kno"n. Each mammalian
chromosome (B0A) contains about .= # longest C basepairs and the double strand is about > cm long. This lengthcould easily be seen "ith the naked eye if the thread "ere
thicker. Inside the cell$ it must be coiled ery tightly.There are three types of 0A that participate in the process of protein synthesis in the cell. All are produced using information
from the B0A in the cell by a process called tran!cription ).
iD Me!!enger #N" ' #N"*: 5arries the genetic code$
"hich specifies the seuence of amino acids in aprotein.
ii. Tran!fer #N" 't #N"*: is a small molecule that sere
as a NshuttleN to bring amino acids to the m-0A in aprocess called tran!lation .
iii. #io!oal #N" 'r-#N"* proides the site for proteinsynthesis by combining "ith protein to make the
ribosome surface that can accept the m-0A molecule.
Mineral! of Biological Significance:
*io-minerals or minerals essential for life are the inorganicnutrients that are needed by liing organisms for italfunctions$ but cannot be synthesi,ed by them. They are
naturally present in the soil and rier "ater. &lants take-upminerals from the soil. Animals get their minerals in drinking"ater and by eating plants as food. 2e receie theseinorganic substances from both animal and plants in our diet.!ometimes$ drinking "ater also supply appreciable uantity of minerals. &urified salts$ such as sodium chloride (0a5l) usedin food preparation$ are also good sources of mineral for human consumption.
Minerals in food and food products are present in both organicand inorganic combinations. Inorganic salts$ such as thephosphates$ carbonates$ chlorides$ sulphates and nitrates of sodium and potassium are common. !alts of organic acids$such as maleic$ o#alic$ acetic$ pectic$ etc. are also found inmost foodfeed and their products.
2hen a foodfeed sample is ignited at high temperature (?-@°5)$ it is completely o#idised and the inorganic carbon freeresidue so left is called a!h. It constitutes the mineral matter and contains element such as sodium$ potassium$ calcium$phosphorus$ sulphur$ etc.
Industrial chemistry is that branch of chemistry "hich deals"ith the chemical processing of ra" material into useful andprofitable products. 5hemical processing may be defined as DThe industrial processing of ra" material leading to the
products of enhanced industrial alue.Safet) Con!i$eration! nece!!ar) in the proce!! of in$u!tr):
. &roper material of construction should be selected bydesigning and chemical engineers in order to preentany loss.
=. To aoid harmful impurities present in ra" materials $
carefully process control by periodic analysis isreuired as "ell as modern instruments should beinstalled.
<. !uitable containers must be proided for supply.>. To ensure safety of "orkers and the plant$ all
procedures must be carried out in non-ha,ardousmanners.
?. To guarantee progress to continue profits and to
replace old processes and euipmentSs. Money shouldbe spent on research and deelopment.
@. To preent contamination of "ater and air$ factoriesmust be "arned to aoid discharge of to#ic materialinto the air and "ater.
A colored substance "hich adds alue to products of their costs is called dye. In most of cases$ color of product isreason of its sale. A $)e is a coloured substance that hasan affinity to the substrate to "hich it is being applied. The
dye is generally applied in an aueous solution$ and reuiresa mordant to improe the fastness of the dye on the fibre.
*oth dyes and pigments appear to be coloured because theyabsorb some "aelengths of light more than others. Incontrast "ith a dye$ a pigment generally is insoluble$ and has
no affinity for the substrate. !ome dyes can beprecipitated "ith an inert salt to produce a lake pigment$ and
based on the salt used they could be aluminium lake$ calciumlake or barium lake pigments.
A dye consists of colour producing structure called the
chromogen or chromopore : electron acceptor;. The solubilityand dying properties called the au#ochrome : electron donor;$"ithout these t"o parts material is simply colourless body.
The chromogen is aromatic containing a color giing group$commonly called the 5hromopore. They act as follo"+
) absorb light in the isible spectrum (>F nm)$
=) hae at least one chromophore (colour-bearing group)$
<) hae a conPugated system$ i.e. a structure "ith alternatingdouble and single bonds.
>) e#hibit resonance of electrons$ "hich is a stabili,ing forcein organic compounds (Abrahart$ H). 2hen any one of
these features is lacking from the molecular structure the
colour is lost.
?) In addition to chromophores$ most dyes also containgroups kno"n as au#ochromes (colour helpers)$ e#amples of "hich are carbo#ylic acid$ sulfonic acid$ amino$ and hydro#yl
groups. 2hile these are not responsible for colour$ their presence can shift the colour of a colourant and they are mostoften used to influence dye solubility
!ome of common chromophores are gien as+
0itroso group 0/ :-0K/7;0itro group 0/= A,o group -0K0-5arbonyl group 5/5arbon-nitrogen 505arbon-sulpher 57<-!7Ethylene group -5K5-
Byes are of many types. Bye may be classified as follo"+. Acid Byes+
!uch kind of dyes are used for dying protein fibers such as"ool$ silk$ nylon$ leather and paper. They contains one or more sulphuric acid substituent or other acidic group.E#ample is acid yello" <@ ( metanil yello").
=. *asic Byes+'sed to dye "ool or cotton as duplicator inks$ carbon paper$type"riter ribbons. In solents other than "ater$ they form"riting and printing inks. *asic dyes are mostly aminocompounds dissoled in acids and made insoluble by the
solution being made basic. E#amples are basic bro"n(*rismark *ro"n) $ basic iolet (crystal iolet).
<. A,o dyes+These are brilliant and long lasting dyes. They are used todye the goods made up of both cotton and "ool or silk. A,odye solubility is generally reduced by adding salt. E#amplesare direct orange =@ and direct black == are typical a,o dyes.
>. Birect Bye+!uch dyes are used to dye the cotton directly$ "ithout adding
any mordant. They are also used to dye union good. Theseare usually a,o dyes and their solubility in the dye bath isreduced by adding salt. Birect orange =@ and direct black ==.
?. Bisperse Bye+!ome fibers such as plastic$ cellulose acetate$ polyesters$0ylon fibers are difficult to dye. Bisperse dyes are ery fineparticles "hich are absorbed on these materials$ and theyform solid solution "ith them. E#amples are disperse red >$
disperse red $ disperse orange =?$ and disperse blue =.@. 6iber-eactie Byes+These dyes react "ith substrate$ usually cellulose to formcoalent bond bet"een dye and fiber like cotton$ rayon andsome nylons are dyed "ith this dye. %inyl sulfone are typicale#ample.
. Mordant Byes and akes+!ome dyes combines "ith metallic salts to form highly
insoluble coloured materials$ called lakes. They are usuallypigments. If a cloth made of cotton$ "ool or other portentousfiber is impregnated "ith lake forming dye$ the metallicprecipitate form in the fiber and color becomes far moreresistant to light and "ashing. The a,o and anthrauinonenucli$ haing attached the groups like /7 and 5//7 can actas mordant dye.
C. !ulphur dyes+
These dyes hae been usedsince long time. They arelarge lo" cost group of dyes"hich produce dull shadeson cotton. The chromophore is comple# and not "ell defined.
!ulphur dyes are usually colorless"hen inthe reduced form in sodiumsulphide bath but gain color ono#idation.
H. !olent dyes+The spirit soluble dyes are usually a,o-triaryl methane are or anthrauinones "hich is organic compound. These are usedto color oils$ "a#es$ arnishes$ shoe polish etc.
. %at-Byes+%at dyeing is a process that refers to dyeing that takes placein a bucket or at. These are "ater insoluble organic pigments$ andbecomes "ater soluble "hen mi#ed"ith po"erful reducing agents. Thereducing operation formerly "ascarried out in "ooden ats. They
hae highly comple# structures andmostly are deriaties of indanthrone. %at dyes are e#pensie and are used on cottoncloths that are subPected to often "ashing and bleaching.!ome ats are applied as pastes for printing. The best kno"ndyes of this class is Indigo$ "hich is one of most popular color in the "orld.
Pe!tici$e!:
&ests amdparaser such as insect$ fungi$ "eeds$ nematodesand bacteria "hich adersely affect the crop plants andreduce yield and uality of the product. 2hen other preentie measures such as cultural$ are inadeuate tosuppress these pests$ then chemicals are used as aneffectie "eapon against the pests and parasites. !uchcompounds$ "hich are inPurious to the pests and protect thecrops from their harmful effects$ are called pe!tici$e!. Theyalso include compounds for the control of rodents$ mites$household and stored products pests.
&esticides are essential tolls of modern agriculture.They form an integral part of the oerall strategy becauseproduction has hardly any meaning "ithout protection. Theyhae changed the prospects of crop production "orld"ide.&esticides hae played a significant role in green reolutionand in increasing crop yield per unit area. They broughtreolutionary change in farm practice. &esticide use indeeloping countries is indispensable in the struggle againsthunger and disease. Emphasis should be gien to Pudicious
and safe use rather than the banning and restriction of pesticides.
According to the plant protection Bepartment of &akistan$ the estimated loss in yield due to pest damageranges from ? to =Q and occasionally it is as high as @ toQ &esticide use in &akistan is based on minimum curatieapplications and on controlling epidemic infections. In&akistan oer Q pesticides are used on cotton and the restmainly on rice$ sugarcane$ fruits and egetables. At present> products comprising oer = actie ingredients areregistered.
CL"SS4C"TON
&esticides may be classified on the basis of their
action against a certain group of organism. They may be+
i. n!ectici$e!+ "hich kill harmful insects$ e.g.
aphids$ grass hoppers and stem-boreres$ etc.
ii. 4ungici$e!$ "hich are used to combatpathologenic fungi (fungal diseases)$ such as rusts
chlorinated eyclodiene and (c) ke#achloroeyclohe#anos (757) (ii) organephosphates+ "hich
are organic esters of phosphoric acid. 2orld used
more than such cmpounds are use as fast
acting systemic pesticides. (iii) 5arbonates+
These are the deriatie of carbonic acid$ actingas nere poison. The "ere discoered in early
H?$ the first chemical product "as carbarye$
marheted by union carnide carparation. They are
used as in sectdes. (i) &yrethsorids+ these are
orlyliid insoluble in "ater and soluble inorganic
solen to pike alcouol and acetone . These
neusoto#ins "ere first obtained from the flo"er of
chrysanthemum species. (5) *ecause of the high
cost of matural pyrothseen$ synthetic compounds
hae been introduced in H@$ "hich are used as
effectie insecticides.
Mire#+It is chlorinated hydrocarbons that "as commerciali,ed as aninsecticides and later on banned because of its harmfulimpact on enironment. This "as deriatie of "hitecrystalline cyclopentadiene.
5hlordane+It is an organic chlorine compound used as pesticide. TillHC< it "as being used in citrus crops$ legumes and asgarden.
7eptachlor+'sed as organochlorine as insecticides. Aailable as "hitetan po"der.
Aldrin+2idely used until H as insecticides.Bieldrin+It "as produced in H>C by L 7yman as insecticides. *oth
dieldrin and aldrin are named after the Bielder reaction "ith isused to form Aldrin.
Petrocheical!:
These are chemical products deried from petroleum.!ome chemical compounds made from petroleum are alsoobtained from other fossil fuels$ such as coal or natural gas$or rene"able sources such as corn or sugar cane.
The t"o most common petrochemical classesare olefins (including ethylene and propylene)and aromatics(including ben,ene$ toluene and #ylene isomers). /ilrefineries produce olefins and aromatics by fluid catalyticcracking of petroleum fractions. 5hemical plants produce
olefins by steam cracking of natural gas liuids likeethane and propane. Aromatics are produced by catalyticreforming of naphtha. /lefins and aromatics are the building-blocks for a "ide range of materials suchas solents$ detergents$ and adhesies. /lefins are the basisfor polymers and oligomers usedin plastics$ resins$ fibers$ elastomers$ lubricants$ and gels.
Global ethylene and propylene production are about ?million tonnes and million tonnes per annum$ respectiely. Aromatics production is appro#imately million tonnes. Thelargest petrochemical industries are located inthe '!A and 2estern Europe3 ho"eer$ maPor gro"th in ne"
production capacity is in the Middle East and Asia. There issubstantial inter-regional petrochemical trade.
&rimary petrochemicals are diided into three groupsdepending on their chemical structure+
• /lefins includes ethylene$ propylene$and butadiene. Ethylene and propylene are importantsources of industrial chemicals and plastics products.*utadiene is used in making synthetic rubber .
• Aromatics includes ben,ene$ toluene$ and #ylenes.*en,ene is a ra" material for dyes and syntheticdetergents$ and ben,ene and toluene for isocyanates MBIand TBI used inmaking polyurethanes. Manufacturers use #ylenes toproduce plastics and synthetic fibers.
• !ynthesis gas is a mi#ture of carbon
mono#ide and hydrogen used tomake ammonia and methanol. Ammonia is used to makethe fertili,er urea and methanol is used as a solentand chemical intermediate.• &rimary precursor petroleum- &etrochemicals
!uspended solids and gases are first remoed from crude oiland it is then subPected to fractional distillation. %ariousfractions of hydrocarbons are obtained at different boilingranges.
"hich is a tough fle#i plastic used to make shopping bags$table cloths$ plastic bottles etc.
87 Poly 9inyl Chloride P9C#+
2hen acetylene is heated "ith 75l at ? o
5 in presence of catalyst$ inyl chloride is produced.
%inyl chloride is "hen subPected to ?=o5 and H atm pressure
it polymeri,es to poly inyl chloride (&%5).
5ommercially this polymeri,ation is carried out in suspension
or emulsion. In emulsion lo" heating is reuired (=o
5)
"hereas is suspension higher temperature is reuired (?-C
o5).
If a plastici,er is added to it$ its fle#ibility increases. It is acheapest plastic used globally. It is used to make pipes$tubing$ garden hoses$ garbage bags$ cable insulations$ fiber manufacturing and gramophone recorders.
Con$en!ation pol)er!+
The polymeri,ation in "hich the monomer molecules areadded after elimination of a small molecule like 7=/$ 75l$
07<$ 57</7 etc$ is called condensation polymeri,ation andthe polymer is called condensation polymer.!aturated monomers polymeri,e to gie condensationpolymers.Their molecular masses are not "hole number multiples of the molecular mass of their monomers.
. Polyester +&olyesters are condensation polymers$ "hich are produced
by condensation polymeri,ation of dicarbo#ylic acid and diol.*ut this polymer has lo" melting point. *ut if an aromatic diester like dimethyl terephthalate (BMT) is polymeri,ed "ith adiol like ethan-$=-diol$ polyethylene terephthalate (&ET&) isobtain. &ET& is a polyester$ its trade name is Terylene. Its
melting point is =@? o
5.
&olymeri,ation is carried out at =-<o5 under a highacuum. Many other polyesters can also be produced. Theyare unattacked by chemicals.
'ses+ They are used to make te#tile fibres. The garmentsmade from theses fibres$ resist the formation of "rinkles.They are used to make carpets.They are used to make magnetic recording tapes.&lastic soft drinks bottles are made from them.
Artificial blood essels and ales are made from them.
=. Polya"ides+These are condensation polymers produced bypolymeri,ation of dicabo#ylic acids "ith diamines. Thesynthetic polyamides are called 0ylons. Their names are
indicated by numbering system e.g. 0ylon produced byhe#amethylene diamine and adipic acid (he#anedioic acid) iscalled 0ylon-@$@.
0ylon-@$@ has good tensile strength$ abrasion resistance andtoughness. It is resistant to many chemicals.
'ses+ It is used as te#tile fibre.It is for production of tyre cords and ropes.It is a good substitute of metals thus is used in gears andbearings.
COSMETCSLip!tic6:ipstick "ere introduced after "orld I. lipstick is the cosmetic"hich is generally formulated to proide both protection ( for the delicate tissues of lips) and color. They are made to beneutral in taste$ stable under normal conditions liketemperature$ moisture$ air flo" and able to preent to#icityand irritation to lip tissues.
Cheical Copo!ition:ipstick chemical composition aries greatly. It may includemi#ture of oils$ "a#es$ pigments$ antio#idants andpreseraties$ sometime perfumes are also added in smalluantity to eradicate the unpleasant smell of oils.
Most of the bulk of lipstick is usually a solid "a#y materialmi#ed "ith a nonolatile oil$ so it can be spread easily butremains stiff in the tube. 5ommon compositions use bees"a#and castor oil$ or carnuba "a#. A recently patentedcomposition uses a solid silicone material "ith polyethylenesolidifier$ and silicone oil.
Many different pigments are used. The dyes hae to be
insoluble in "ater$ so the color "ill last. !oluble dyes are firstNlakedN$ that is$ conerted to insoluble particles by treatment"ith metal o#ides. Eosin is a commonly used red dye inlipsticks+
Eosin$ the red pigment in lipsticks.GrayK5arbon$ edK/#ygen$*ro"nK*romine.5lick the image for a <B 5himemodel.
It becomes an intense red "hen it reacts "ith 07 = groups inproteins on the surface of the skin. The pigment is masked inthe tube by a laked green or blue dye$ and the color change"hen the lipstick is applied to the skin is sharp.
Many other ingredients insure that the lipstick has the proper
te#ture and melting point. 6or e#ample$ esters of fatty acids(myristates) are sometimes added to gie the lipstickNstickinessN.
Characteri!tic!:
• it should be nonirritating and nonto#ic
• it should be stable both physically and chemically.
• it should not dry on storage.
• it should be free from gritty particles.
• it should maintain lip colour for longer period after itsapplication.
• it should gie shiny and smooth appearance free froms"eating.
that can be applied to thehuman fingers or toe nails
to decorate and protect the nailplate
. The formulation has been reised repeatedly toenhance its decoratie effects and to suppress cracking or flaking. 0ail polish consists of an organic polymer "ith ariousaddities. 0ail polish originated in 5hina$ and its use datesback to < *5. Around @ *5$ during the 9hou dynasty$the royal house preferred the colors gold and siler. 7o"eer$
red and black eentually replaced these metallic colors asroyal faorites. Buring the Ming dynasty$ nail polish "as oftenmade from a mi#ture that included bees"a#$ egg"hites$ gelatin$ egetable dyes$ and gum Arabic.
In Egypt$ the lo"er classes "ore pale colours$ "hereas highsociety painted their nails red.
*y the turn of the Hth century$ nails "ere tinted "ith scentedred oils$ and polished or buffed. In the Hth and early =thcenturies$ people pursued a polished rather than a paintedlook by massaging tinted po"ders and creams into their nails$then buffing them shiny. /ne such polishing product soldaround this time "as GrafNs 7yglo nail polish paste.
Traditionally$ nail polish started in clear$ red$ pink$ purple$ andblack. !ince that time$ many ne" colors and techniues hae
deeloped$ resulting in nail polish that can be found in ane#tremely dierse ariety of colors. *eyond solid colors$ nailpolish has also deeloped an array of other designs$ such ascrackled$ speckled$ iridescent$ and holographic3 rhinestonesor stickers are also often applied. !ome types of polish areadertised to cause nail gro"th$ make nails stronger$ preentnails from breaking$ cracking and splitting$ and to stop nailbiting. 0ail polish may be applied as one of seeral
"ith the solent and other ingredients is essential to
producing a good uality product.
Nail Poli!h #eo(er:
A nail polish remoer is an organic solent that is used toremoe preiously applied nail polish from nails. There are
many different types of remoers on the market and differentbrands may hae different chemical compositions. Theprinciple ingredients in most$ ho"eer$ are acetone$ethyl acetate or butyl acetate$ and alcohol.These chemicals are kno"n to dehydrate the skin$ causeirritation to eyes$ and make nails dry and brittle. They alsohae a distinct chemical smell and are highly flammable. Tocounter the dehydration and brittleness effects$ manyremoers also contain conditioning ingredients like castor oil$cetyl palmitate$ or lanolin.
!ome remoers are acetone-free$ but this does notnecessarily mean that the product is "ithout side effects$ soshoppers should screen the ingredients list carefully. Insteadof acetone$ the nail polish remoer may contain the more
to#ic methanol. 5onsumers looking for safer and less-to#icoptions can opt for "ater-based products.
or6ing
To understand ho" nail polish remoer "orks$ it is necessaryto kno" that fingernail polish and the remoer both contain
similar organic solents3 the nail polish also contains dryingagents$ thickeners$ hardening agents$ and coloring agents.The organic solent in a nail polish is "hat keeps it in a liuidstate. A solent in the remoer is "hat dissoles the hardenedpolish and returns it back into its liuid form. 2hen the
remoer is applied to the nail polish$ the molecules interrupt$
loosen$ and break the polymer
chains of the polish. Thisdissoles the hardened polish and transforms it back into itsoriginal liuid form so that it can then be "iped off the nail.
air 0)e!
It is the practice of changing the color of hair. The main
reasons for this practice are cosmetic (e.g.$ to coer gray hair$
to change to a color regarded as more fashionable or desirable$ or to restore the original hair color after it has been
discolored by hairdressing processes or sun bleaching). 7air dyeing$ "hich is an ancient art$:;
inoles treatment of the hair "ith arious chemical compounds. 7air color "as traditionally
applied to the hair as one oerall color. The modern trend isto use seeral colors to produce streaks or gradations$ not all"ork on top of a single base color. These are referred to as+
T)pe! of hair coloring
The four most common classifications are permanent$ demi-
permanent (sometimes called deposit only)$ semi-permanent$
and temporary.
1D Peranent hair color
A ery popular "ay to achiee permanent hair coloring isthrough the use of o#idation dyes. The ingredients of these
products include $>-diaminoben,ene (historically) or =$?-diaminotoluene (currently)$ a coupling agent$ and an o#idant.The process is typically performed under basic conditions.
The preparation (dye precursors) is in the leuco ("hich
means colorless) form. /#idi,ing agents are usually hydrogenpero#ide$ and the alkaline enironment is usually proided by
ammonia. The combination of hydrogen pero#ide and theprimary intermediate causes the natural hair to be lightened$proiding a Rblank canasR for the dye. Ammonia opens the
hair shaft pores so that the dye can actually bond "ith the
hair and speeds up the reaction of the dye "ith the hair. 0o"people can dye their hair "ithout bleaching it.
%arious combinations of primary intermediates and couplersproide a spectrum of shades of hair colors. The primary
intermediates are aromatic para compounds$ such as $>-
diaminoben,ene or >-aminophenol. The couplers are meta-substituted deriaties of aniline. They come in three maPor
classes based on the color that they produce "hen they react"ith the primary intermediate.
5ouplers are chemical compounds that define the color of the
hair dye. !ho"n here are three red couplers (A$*$5)$ t"oyello"-green couplers (B$E) and a blue coupler (6).
• *lue couplers include $<-diaminoben,ene and its
deriaties.
• ed couplers include phenols and naphthols$ such as
<-aminophenol (5A!?H-=-?)$ ?-amino-=-methylphenol(5A!=C<?-H?-=) and -naphthol (5A!H-?-<). Thecombination of =$?-diaminotoluene "ith the coupler <-
aminophenol gies a magenta-bro"n dye$ "hile thecombination of =$?-diaminotoluene "ith the coupler -naphthol gies a purple dye.
• Uello"-green couplers include resorcinol$ >-chlororesorcinol$ and ben,odio#oles. These compoundsproduce broad-band absorption "hen they react to form dyes$
allo"ing for more natural-looking hair colors. The combinationof =$?-diaminotoluene "ith the coupler resorcinol gies agreenish bro"n dye.
The first step sho"s the o#idation of p-phenylenediamine to
This species e#ists in euilibrium "ith the monoprotonated
form (5@7>(07)(07=)) (not sho"n). The second step inolesthe attack of this uinonediimine on the coupler. In organic
chemistry$ this reaction is calledelectrophilic aromaticsubstitution+
In the third and final step$ the product from the
uinonediimine-coupler reaction o#idi,es to the final hair dye.
The resulting hair dye is also much larger than the precursor
molecules$ "hich causes the dye to bond to the hair.
9D 0ei-peranent hair color
Bemi-permanent hair color is hair color that contains analkaline agent other than ammonia(e.g. ethanolamine$ sodium carbonate) and$ "hile al"aysemployed "ith a deeloper$ the concentration of hydrogen
pero#ide in that deeloper may be lo"er than used "ith apermanent hair color. !ince the alkaline agents employed in
demi-permanent colors are less effectie in remoing thenatural pigment of hair than ammonia these products proideno lightening of hairNs color during dyeing. As the result$ theycannot color hair to a lighter shade than it "as before dyeing
and are less damaging to hair than their permanent
counterpart.
Bemi-permanents hae seeral adantages as compared"ith permanent color. *ecause there is essentially no lifting(i.e.$ remoal) of natural hair color$ the final color is less
uniformhomogeneous than a permanent and therefore morenatural looking3 they are gentler on hair and therefore safer$especially for damaged hair3 and they "ash out oer time
(typically = to =C shampoos)$ so root regro"th is lessnoticeable and if a change of color is desired$ it is easier toachiee. Bemi-permanent hair colors are not permanent but
the darker shades in particular may persist longer than
indicated on the packet.3D Sei-peranent hair $)e
!emi-permanent hair color has smaller molecules than
temporary dyes. These dyes only partially penetrate the hair shaft. 6or this reason$ the color "ill surie repeated "ashing$typically >F? shampoos or a fe" "eeks. !emi-permanents
contain no$ or ery lo" leels of deeloper$ pero#ide or ammonia$ and are therefore safer for damaged or fragile hair.7o"eer$ semi-permanents may still contain the possibly
carcinogenic compound p-phenylenediamine or other suchingredients. The '.!. Enironmental &rotection Agencyreported that in rats and mice chronically e#posed to &&B in
their diet$ it simply depressed body "eights$ and no other clinical signs of to#icity "ere obsered in seeral studies.
The final color of each strand of hair "ill depend on its original
color and porosity$ so there "ill be subtle ariations in shadeacross the "hole head. This gies a more natural result than
the solid$ all oer color of a permanent color. 7o"eer$ it alsomeans that gray or "hite hairs "ill not appear as the sameshade as the rest of the hair. If there are only a fe" grey"hite
hairs$ the effect "ill usually be enough for them to blend in$
but as the gray spreads$ there "ill come a point "here it "illnot be disguised as "ell. In this case$ the moe to permanent
color can sometimes be delayed by using the semi-permanent as a base and adding highlights.
!emi-permanent color cannot lighten the hair.
@D Teporar) hair color
Temporary hair color is aailable in arious forms includingrinses$ shampoos$ gels$ sprays$ and foams. Temporary hair
color is typically brighter and more ibrant than semi-permanent and permanent hair color. It is most often used tocolor hair for special occasions such as costume parties .
The pigment molecules in temporary hair color are large andcannot penetrate the cuticle layer. The color particles
remain adsorbed (closely adherent) to the hair shaft and areeasily remoed "ith a single shampooing. Temporary hair color can persist on hair that is e#cessiely dry or damaged in
a "ay that allo"s for migration of the pigment to the interior of the hair shaft.
The branch of chemistry "hich deals "ith pollutants$ their to#ic effects and solution to pollution problems is calledenironmental chemistry. .
Earth "hen formed about >.? billion year ago$ "as ery hotand there "as no life on it. *ut then it started cooling. !teamcondensed to "ater$ atmospheric gas formed$ o,one layer
formed in stratosphere. 2ith this$ earth became suitable for life. ife "as peaceful but "hen industries and machines "eredeeloped pollution problems started$ "hich are becoming"orse day by day.
Coponent! of En(ironent+
(i) *ithosphere+
The upper rocky crust of earth "hich e#tends to the depth of km$ is called lithosphere. It includes soil$ minerals andorganic matter present in the earth crust.Total land aboe sea leel is <@.@ billion acres$ out of "hich billion acres are directly useable by man. About @ billionacres are used for agriculture. *ut agricultural land isdecreasing due to erosion and urbani,ation by increasing
population.
5omposition of lithosphere is/ >@.@Q!i =.=Q
Al C.<Q6e ?Q5a <.@<Q
0a =.C<Q4 =.?HQMg =.HQTi$71& Q51 trace elements .=-.Q
%arious forms of "ater on earth$ make hydrosphere.These include oceans$ lakes$ riers$ streams$ sno"$ glaciers$polar ice caps and ground "ater reseroirs i.e. "ater belo"earth surface.
Q of earthSs surface is coered "ith oceans and <.?Qby polar ice. HQ of earthSs "ater is contained in oceans$ =Q
by polar ice and glaciers "hile only Q is fresh "ater (ground"ater$ lake$ rier$ stream etc). 2e use fresh "ater for agriculture$ industry$ transport and domestic purposes.
(iii) ,iosphere+
The region of the earth "hich supports life is calledbiosphere. It includes lo"er atmosphere$ oceans$ riers$
lacks$ soil and solid sediments that interchange materials "ithall type of liing organisms.*iosphere can also be defined as the place "here liing
organisms interact "ith other earth system.Ecosystem is smaller unit of biosphere$ "hich consists of
community of liing organisms and their interaction "ithenironment.
(i) -t"osphere+
Enelop of gases that surrounds the earth surfaceis called atmosphere. It is e#tended to kmaboe earthSs surface. 7alf of its mass isconcentrated in lo"er ?.@ km. It contain
Atmosphere maintained life on earth. /= is reuired for breathing$ 0= is used by nitrogen fi#ing bacteria$ 5/= is usedby plants for photosynthesis$ "ater apours for sustaining life.
Atmosphere saes life from hostile enironment of outer space. It absorbs cosmic rays$ '.% rays coming from outer space.It maintains heat balance of the earth. It is responsible for hydrological cycle ("ater from oceans to land and back tooceans).
The atmosphere is diided into four spheres+(a) Troposphere+ It e#tend from -km. The
temperature ranges from ? to -?@o5.
It decreases "ith altitude.
It constitutes Q of the atmosphere.It contains 0=$ /=$ 5/=$ "ater apours.
Its temperature falls "ith increase inaltitude.
(b) Stratosphere+ It e#tends from -? km.
Its temperature ary from -?@ to -= o
5.Its temperature increases "ith altitude.Its important constituent is o,one /<. Itstemperature increase "ith increase in altitude/,one layer is a shield against '.% rays
increases "ith increase in altitude. 7ereelectromagnetic radiations change the gases toplasma state.
uan interaction /ith en(ironent+7uman is in continuous interaction "ith enironment.
Man needs o#ygen$ food$ space$ shelter$ cloths and energy.In beginning humanSs life "as ery simple but "ith passage of time he deeloped industries$ transport means "hich hae
made enironment unfriendly due to pollution caused bythem. /ne should seriously think about it.
"ir Pollution+
The air is polluted "hen harmful substances "hichdamage the enironment$ human health and uality of life aremi#ed in it. The pollutants (solid$ liuid$ gases) trael through
air due to circulation of air and reach to oceans other placesand man. Gases gradually accumulate in the air andeentually reach to the leel beyond T%s (threshold limitalues) and thus become pollutants.DGases and other substances that accumulate in air andreach beyond threshold limit alues are called pollutants.
D&resence of pollutants or contaminants in air is called air pollution.The pollutants of air are dust$ grits (tiny pieces of stones)$fumes$ gas efferescence$ mist fog$ smog$ soot$ smoke$cloud$ poly aromatic hydrocarbons (&A7)$ poly acylnitrates(&A0) and apours etc.
Types of &ollutants+
&ollutants are diided into t"o categories+
&rimary pollutants+ The substances that are directlyemitted from sources are called primary pollutants e.g. 7=!$!/=$ 0/$ 07<$ 76$ 75l$ 5/$ 5/= etc.
!econdary pollutants+ The substances that are formed in theatmosphere by chemical interactions amongst primarypollutants are called secondary pollutants e.g. 0/=$ !/<$7=!/>$ ketones and o,one.
!ources of &ollutants+!ources of pollutants are diided into t"o categories+
() 0atural source+ It includes all "ind blo"n or "indassisted pollutants like sea salt$ smoke gases$ forest fires andolcanic gases.
(=) Anthropogenic source+ It includes pollutants gien byman made industrial actiities$ po"er plants$ fuel burning inautomobiles.
So"e "ain air pollutants+1D Caron Mono.i$e+
It is colourless$ odourless gas. It is three times lighter than air. It is slightly soluble in "ater.
It is highly to#ic and is asphy#iant gas. (The gas "hich makessome one unable to breath and can cause death is called
asphy#iant gas). 5/ get bonded to haemoglobin morestrongly than /= so o#ygen thus e#cludes from respiration.E#posure to 5/ results in headache$ fatigue$unconsciousness and eentually to death if e#posure is for longer time. 5/ poisoning can be reersed by giing highpressure o#ygen.
Sources+
0atural sources+ Its natural sources are olcanic eruption$natural gas emission and o#idation of methane in air.Methane is also formed during decay of organic matter and itthen on o#idation in air produces 5/.
Anthropogenic source+ It is mainly produced by incompletecombustion of carbonaceous materials. Its chief sources aree#haust from automobile$ rail"ay$ aircrafts and burning of coal. *eside these other sources are industries e.g. iron (blastfurnace operation)$ petroleum$ cement etc. 9D Sulpher $io.i$e+
It is colourless gas. It has pungent smell so is irritating
and suffocating. In air it produces sulphate aerosols "hichcauses respiratory troubles particularly in older people. It iscause of acid rain also.
Sources+
0atural sources+ It is produced by olcanoes$ also byo#idation of organic matter.
Anthropogenic source+ It is produced by burning coal$ crudecoal oil and other fossil fuel.
3D O.i$e! of Nitrogen 'N.O)*+The o#ides are 0itric o#ide(0/)$ 0itrous o#ide(0=/)
and 0itrogen dio#ide(0/=)./#ides of nitrogen are second most abundant atmosphericcontaminants.
Sources+
0atural sources+ Becay of dead organisms.
Anthropogenic source+ It is produced by burning fossil fuel(nitrogenous compounds are present in these fuels)$ bacterialaction on fertili,ers.
@D Cou!tion of h)$rocaron a!e$ fuel!+ The hydrocarbon based fuels are solids$ liuids andgases. e.g. coal is solid fuel$ 4erosene oil$ gasoline$ diesel$
furnace oil etc are liuid fuels$ 0atural gas$ coal gas etc aregaseous fuels.These fuels beside 5/$ !/#$ 0/# also produce follo"ingpollutants
(a) &articulate matter Aerosols+ Microscopic si,e solid or liuid particles dispersedin gaseous media are called aerosols e.g. mist$ fog$ dust etc.
Aerosols aries in si,e from .m to m.It is produced
Bust+ It is produced by crushing and grinding coal. 6ly ashfrom chimney also produce dust.
!moke+ It is produced by incomplete combustion. It is mainlyconsists of carbon particles. !i,e of smoke particles is lessthan m. TM and TE used as antiknocks on burning of fuel produce lead (a particulate matter) in the smoke.
(b) 5arbon Bio#ide+It is produced by combustion of fossil fuel$ decay of organicmatter etc.5/= causes green house effect and thus global"arming.
(c) 7ydrocarbons+ %ehicles emit hydrocarbons including poly-aromatic hydrocarbons (&A7s) in air.
The %reen ou!e Effect
The greenhouse effect is a process by "hich thermalradiation from a planetary surface is absorbed byatmospheric greenhouse gases$ and is re-radiated in all
directions. !ince part of this re-radiation is back to"ards thesurface and the lo"er atmosphere$ it results in an eleation of the aerage surface temperature aboe "hat it "ould be in
planetary surface$ "hich then emits this energy at the lo"er freuencies of infrared thermal radiation. Infrared radiation isabsorbed by greenhouse gases$ "hich in turn re-radiate
much of the energy to the surface and lo"er atmosphere. The
mechanism is named after the effect of solar radiationpassing through glass and "arming a greenhouse$ but the
"ay it retains heat is fundamentally different as a greenhouse"orks by reducing airflo"$ isolating the "arm air inside thestructure so that heat is not lost by conection. If an ideal
thermally conductie blackbody "ere the same distance from
the !un as the Earth is$ it "ould hae a temperature of about?.< O5. 7o"eer$ since the Earth reflects about <Q of the
incoming sunlight$ this ideali,ed planetNs effectietemperature (the temperature of a blackbody that "ould emitthe same amount of radiation) "ould be about qC O5. The
surface temperature of this hypothetical planet is << O5 belo"
EarthNs actual surface temperature of appro#imately >O5. The mechanism that produces this difference bet"een the
actual surface temperature and the effectie temperature is
due to the atmosphere and is kno"n as the greenhouse
effect.
EarthSs natural greenhouse effect makes life as "e kno" itpossible. 7o"eer$ human actiities$ primarily the burning of fossil fuels and clearing of forests$ hae intensified the natural
greenhouse effect$ causing global "arming.
*y their percentage contribution to the greenhouse effect onEarth the four maPor gases are+
• "ater apor $ <@FQ
• carbon dio#ide$ HF=@Q• methane$ >FHQ
• o,one$ <FQ
The maPor non-gas contributor to the EarthNs greenhouseeffect$ clouds$ also absorb and emit infrared radiation and
thus hae an effect on radiatie properties of the atmosphere
Effect of Pollute$ air on En(ironent+. -cid Rain+
p7 of clean rain (unpolluted rain) is ?.@ as itcontain 5/= of atmosphere$ *ut acid rain is theone "hose p7 is belo" ?.@ upto =.DAll precipitations i.e. rain$ sno"$ de" etc that haep7 belo" ?.@ are called acid rain.
In unpolluted rain 5/= is dissoled producing7=5/< thus its p7 is [email protected]/= 7=/ J 7=5/<
The acid rain on other hand has p7 less than [email protected] uantities of sulphur and nitrogen o#ides areemitted into atmosphere from the chimneys of
arious industries. The o#ides of sulphur and thatof nitrogen produce 7=!/> and 70/< respectiely.
!/= /= 7=/ J 7=!/>
0/= 7=/ J 70/<
Bue to acid rains "ater of streams$ lakes etcbecome acidic and it then harms auatic life. It killsfishes$ reduces their gro"th and reproductiity. Italso preent hatching of fish eggs. Green algaeand other beneficial bacteria$ "hich are essential
for auatic life are killed.It is threat to human health also as drinking "ater becomes contaminated.It effects plant gro"th also.It corrodes buildings$ monuments$ statues andmetals.
=. S"og +
!mog is combination of smoke and fog. Appearance of bro"nish colouration inatmosphere is due to smog. 2orse disaster occurred in ondon in H?=$ 2hen on Thursday$ >Becember H?= a cold- air mass enter alley of ier
Themes. Then on !aturday smog completely
coered ondon$ that "as a dark day. /n Mondayabout people "ere died. ater on > to? death occurred due to smog. Minor disastersalso reported in os Angles (in forties)$ Mousealley (*elgium) H<.
There are t"o types of smog.(i) &hotochemical smog+
The smog "hich is caused by o#ides of nitrogen and hydrocarbons is calledphotochemical smog or os Angeles smog.The cities "here there is heay traffic(Automobiles)$ during combustion of fuel at
high temperature$ beside fuel 0= of air alsoreacts "ith /= and produces 0/. The 0/emits to air in e#haust.
0= /= J =0/In air 0/ reacts "ith /= to produce 0/=$ "hichis of bro"n colour. It irritates eye and damagesthe respiratory tract.
=0/ /= J =0/=
2hen 0/= e#posed to sunlight$ it is conerted
into 0/ and atomic o#ygen0/= J 0/ /The atomic o#ygen reacts "ith molecular o#ygen and produces o,one. It irritates eyesand respiratory tract. It cause coughing andfatigue. It also causes deterioration of fabrics.It cracks rubber and damages plants andcrops.
(ii) Industrial smog+!ome time it is also called reducing smogor ondon smog. It is caused by !/=. It isproduced in areas "here coal is burnt in largescale. /n combustion$ the sulphur contentsproduce !/=.
! /= J !/=
It irritates eyes$ causes lungs and respiratory
diseases. It suppresses plant gro"th and iscorrosie to metals.It further reacts "ith /= of air produces !/<
"hich dissole in "ater and produces 7=!/>
and thus causes acid rain.=!/= /= J =!/<
!/< 7=/ J 7=!/>
<. Ozone+It is a gas present in stratosphere (? to ? kmaboe earth surface). It filters '.% rays andprotects us. *ut if present in lo"er atmosphere it
has aderse effects. 2hen 0/= e#posed tosunlight$ it is conerted into 0/ and atomic o#ygen
0/= J 0/ /The atomic o#ygen reacts "ith molecular o#ygenand produces o,one. It is produced in tropicalregions and transported to &olar egions.It causes irritation of eyes$ asthma$ coughing$chest discomfort etc. It is harmful to plants andother materials also.
Bepletion (reduction or decrease in oerheadamount) of o,one is occurring "orld "ide butespecially oer Antarctica. 7ere by the mid HCs$?Q depletion of ,one occurred. It is called o,onehole.The pollution of air by 6reon or chlorofluorocarboncompounds (565s) is the main cause of o,onedepletion. 565s are used as refrigerants$ they are
inert in troposphere but they diffuse intostratosphere "here they are e#posed to '% raysand produce 5l free radical "hich reacts "itho,one.
565l< J 565l= 5l.
5l. /< J 5l/
. /=
5l/. / J 5l. /=
ater Pollution+2ater is essential for life. 2ater gets contaminated due to&hysical$ *iological and 5hemical pollution. A fe" of themare follo"ing+
-gricultural Waste+These include pesticides$ fertili,ers and heay metals. 0o" adays farmers are using large uantities of pesticides andfertili,ers to get good crops. They make their "ay to ground"ater by leaching "ith rain "ater and to riers and streams by
. /ccluded gases like 5/$ 5/=$ 7=!$ 750$ 5/! etc.=. Bissoled gases like 07<
<. Inorganic salts like carbonates$ bicarbonates$sulphates$ sulphides etc.>. /rganic compounds like ben,ene$ toluene$ phenol$
#ylene etc.?. &athogens
&aper Industries$ metal Industries and petrochemicalIndustries add degradable organic pollutants to "ater.Tanneries (leather industries) gie effluents "ith dark colour
and ery bad smell$ high */B and high salinity. 4=5r =/ usedin tanning is highly to#ic and is cancer causing. Arsenic isalso used for hair remoal from hide. *oth arsenic andchromium are not suitable for drinking "ater. The other serious problem that tanneries gie is smell nuisance.!laughterhouses$ te#tile industries also gie "ater pollution.
(o"estic or 2unicipal Waste+
It is important source of "ater pollution. Bomestic "ater mainly contains soap and detergents. Bomestic "ater causesfollo"ing effects on fresh "ater pollution
. It causes turbidity and effect auatic life.=. It is a source for gro"th of pathogens.<. It gies bad smell to fresh "ater due to haing
nitrogenous matter in it.
>. Betergents in it hae phosphates "itch stimulatealgae gro"th. Algae coers the "ater surface and cutsunlight "hich is threat to auatic life.
?. It contains suspended matter "hich also blockssunlight to auatic life.
&etroleum leaked from ships spread on "ater. It affectsphotosynthesis and dissoled o#ygen$ also birds "hen die insearch of fishes$ their feathers clogged "ith oil and then theycannot fly and ultimately many of them may die.Many petroleum products are poisonous and cause healthproblems to humans$ animals and auatic life. 7ydrocarbons
particularly polycyclic aromatic compounds are carcinogenic.*i%estoc. Waste+
Mostly liestock "aste is either dumped on open land or discharged to canals$ riers etc. It causes infectious diseaseslike dysentery$ typhoid and hepatitis.
Pesticides+They are insecticides$ herbicides and fungicides used to killinsects$ herbs and fungus. *eside it they also helped in theeradication of malaria$ yello" feer$ sleeping feer etc. *ut "hen$ they get to fresh "ater$ cause serious problems tohuman and animals.
ater ualit)+
Brinking "ater should possess follo"ing ualities+. It should be colourless and tasteless.
=. It should be free from turbidity i.e. turbidity should note#ceed ppm. Turbidity of "ater is caused bysuspended solids$ dissoled solid$ chlorides$
sulphates$ phosphates etc.<. Its p7 should be in range of . F C.?.>. It should be free from disease causing bacteria and
So"e of para"eters used to chec. the 4uality of water are+
. Bissoled o#ygen (B/)+ Its concentration in"ater is > F C ppm. It o#idi,es organic matter dissoled in "ater. If its concentration is less than >ppm then "ater is polluted.
=. *iological*iochemical /#ygen Bemand (*/B)+ Itis the capacity of organic matter in natural "ater toconsume o#ygen "ithin a fie days period. A sealed
"ater sample is maintained in dark at = F =?o5. Thereaction is cataly,ed by bacteria. Amount of o#ygenconsumed is measured after fie days.
<. 5hemical /#ygen Bemand (5/B)+ The organiccontent of "ater "hich consumes o#ygen duringchemical o#idation is ealuated by 5/B. It ismeasured by treating "ith 4=5r =/ (strong o#idi,ingagent). The organic mater is o#idi,ed and remainingdichromate is determined by titration. 5/B is ameasure of chemically o#idi,able matter in "ater. 7igh5/B alu indicates more pollution.
>. Total /rganic 5arbon (T/5)?. Total Bissoled !olid (TB!)@. Total !uspended !olid (T!!). p7
C. 5olour H. /dour . *acteriological measurement etc
Preparation of Potale ater +
Ground "ater is comparatiely clean than surface"ater. !o$ surface "ater needs treatment to make it fit for
drinking purpose (potable). 6ollo"ing methods are used for "ater treatment to make it potable (safe and fit for drinking)+
. Screening and filtration+6loating and isible solids present in "ater are
remoed by screeningfiltration. 5ross linked iron bars may
sere as screen. 6loating solids are held by screen and "ater pass through. =. -eration+
Air is passed through "ater to remoe dissoledgases like 7=!$ organosulphur compounds and olatileorganic compounds. Aeration also o#idi,es soluble 6e= to6e< "hich then forms 6e(/7)< and is remoed as precipitate.
Aeration also increase dissoled o#ygen in "ater.
<. Coagulation+5olloidal substances are remoed by coagulation$
flocculation and sedimentation processes. Alum or Aluminium sulphate (coagulants) is added for this purpose. If natural alkalinity is not present in the "ater$ then lime:5a(/7)=; or sodium carbonate must be added. In alkalinemedium follo"ing reactions occurZ
4=!/>.Al=(!/>)<.=>7=/ <5a(/7)= J <5a!/> =Al(/7)<_ 4=!/> =>7=/ Al=(!/>)< 5a75/< J <5a!/> =Al(/7)<_ @5/= The colloidal substances adsorbs on the surface of gelatinousprecipitate of aluminium hydro#ide.
>. (isinfection of Water by Chlorine+5hlorination of "ater is carried out to kill disease
causing bacteria and other pathogens. /ther candid (fair)techniues to kill pathogens are o,onation and '%
irradiation. *ut chlorination is "idely used techniue. 5hlorinereacts "ith "ater producing hypochlorus acid
5l= 7=/ J 7/5l 7 5l-
7ypochlorous acid the decomposes and gies nascento#ygen "hich kills pathogens. 7/5l J 75l /
Addition of e#cess of chlorine is called *reakthrough5hlorine$ it is carried out for satisfactory disinfection of "ater.
7o"eer chlorination cannot kill iruses$ also it cannotremoe taste and odour neither it can o#idi,e organiccompounds in "ater.
a!te Manageent+
In past "hen no industries "ere deeloped$ "astematerial "as only domestic "astes and agricultural "astes"hich "ere easily disposed in country sides.
*ut no" "aste material are dierse materials and their disposal is a problem.
(u"ping wastes in sea and ri%ers+ Bumping "astes in seaand riers is a common practice. 2aste contain to#ic
chemicals "hich is threat to auatic life. The "aste alsocontain radio actie material$ metals$ debris$ e#plosies$garbage and many more. All these are harmful to auatic lifeas "ell as human (indirectly). Many disasters such as deaths
occurred at &ort of Manimata (Lapan) due to Minimatadisease caused by eating of mercury contaminated fishes. Pla!tic> Paper an$ Metal a! !oli$ /a!te+
&lastic use is ery spread no"-a-days. &lastic becamelarger part of municipal solid "aste (M!2) and is a problem.
&aper is also ery e#tensiely used for arious
purposes and its disposal is a problem.Metals are used for packing e.g. Aluminium
and tin cans are used for packing foods$ egetable ghee$ drymilk etc. Bisposal of "hich$ affected landfills capacity andcreated isual pollution.
6locculation is related to destruction of colloidal sol. The
aggregation of particles is called coagulation and resultingsedimentation is called flocculation.!o aggregation of destruction of colloidal sol is calledcoagulation and resulting sedimentation part is calledflocculation.
%reen chei!tr)$It is also called !u!tainale chei!tr)$ is a philosophy of
chemical research and engineering that encourages thedesign of products and processes that minimi,e the use andgeneration of ha,ardous substances.:; 2hereas enironmental chemistry is the chemistry of the
natural enironment$ and of pollutant chemicals in nature$green chemistry seeks to reduce the impact of chemistry on
the enironment by preenting pollution at its source andusing fe"er natural resources.
uantitatie analysis seeks to establish the amount of agien element or compound in a sample.
E#ample3 The ualitatie and uantitatie analysis canunderstand from e#ample of Dpollutant "hich the killing thefish in a rier
In such a case analyst hae to determine first the chemicalidentity of a said pollutant. !o by means of Dualitatieanalysis 7e can e#plore "hether the pollutant is a heaymetal ( &b. 5d$ 7g and 0i etc) or some other substance.
/nce the chemical identity of the concentration (uantity) of that pollutant in the sample (rier) by Duantitatie analysisi.e if it is obsered that the rier pollutant is mercury (7g) thenits concentration can easily be estimated
B* NST#MENT"L METO0S
Instrumental Analysis depends on instrument of some sort$either to make a critical measurement during as analysis to
be performing the entire analysis.E#ample3 if the endpoint of the titration of 75 "ith 0a/7 islocated "ith an Dinstrument Analysis
Cou!tion "nal)!i!:It is one of the estimation techniues. A "eighed amount of sample is placed in combustion tube. The tube is connectedto cylinder of o#ygen gas and the gas is passed for some timeto remoe air from the combustion tube.
The t"o u-shaped tubes$ one containing "ater absorber andother containing 5/= absorber are "eighed and connected tothe combustion tube as sho"n in fig. The compound in the
combustion tube is strongly heated to burning. 5arbon andhydrogen (if any) of the compound "ill be conerted to 5/ =
and 7=/ respectiely. The increase in the "eight of absorbers"ill gie the mass of 5/= and 7=/ produced. 6rom the massof 5/= percentage of 5arbon is calculated "hile from themass of 7=/ percentage of 7ydrogen is calculated.I.Calculations of /"perical 0or"ula+
These calculations inole follo"ing steps!tep- Amounts of elements present in the compound aredetermined.!tep-= Moles of elements are calculated.!tep-< !imple molar ratio is calculated by diiding moles of
each by lo"est number of moles.!tep-> If simple molar ratio is not in "hole numbers$ it iseither rounded or multiplied "ith some suitable number to get"hole number ratio.
!tep-? !ymbols of the elements are "ritten "hile their corresponding numbers are "ritten in subscripts. esultingformula is empirical formula.
II. (eter"ination of 2olecular 2ass+Molecular mass is determined e#perimentally. %arioustechniues are aailable for this purpose$ "hich includeeleation of boiling point$ depression of free,ing point$lo"ering of apour pressure$ %ictor Meyer method etc.
III. Calculations of 2olecular 0or"ula+These calculations inole follo"ing steps!tep- Emperical formula mass is calculated.!tep-= atio bet"een molecular mass and empirical formulamass is calculated.
!tep-< Molecular formula is calculated asMolecular formula K n # empirical formula
Molecular "!orption Spectro!cop):
Molecular absorption spectroscopy$ particularly in the
isible region (>-? nm) of EM$ is based on *ear-lambertsla"$ "hich states that absorption of light by coloured solution isproportional to (a) the number of molecules (concentration) of the absorbing compound$ and (b) the length of the light path(i.e. the area through "hich light passes). Mathematically thisstatement can be "ritten as+
A 5
AK k.5.l
2here A K absorbencyk K is a constant$ "hich aries "ith the nature of
5 K concentration of compound in molliter.l K length of the light path$ "hich is usually l cm.
Thus if l and k are the same$ that is the samecompound is tested in the same light-path$ then+ AK 5
This sho"s that keeping other factor constant$absorbency is eual to the concentration of the absorbingcompound in solution.
As different compounds hae different absorptionma#ima$ hence *ear-ambertSs la" holds strictly for monochromatic radiation (that is for radiation "ith a narro"band of "aelengths).
Many system in dilute solution follo" *ear-ambertSsa"$ ho"eer$ absorbance aries in a non-linear manner "ithrespect to concentration. !uch behaiour is called a deiation
from *ear-ambertSs a". True deiations occur only "hen theconcentration of absorbing species is so high that the inde# of refraction for the absorbed radiation is changed. 5onseuently$solutions "ith concentration belo" -= M should be used inmolecular absorption spectroscopy.
nfrare$ #Infrared spectroscopy (I !pectroscopy) is the subset
of spectroscopy that deals "ith the I region of the EMspectrum. It coers a range of techniues$ "ith the mostcommon type by far being a form of absorption spectroscopy.
As "ith all spectroscopic techniues$ it can be used to identifya compound and to inestigate the composition of a sample.
The infrared portion of the electromagnetic spectrumis diided into three regions3 the near-$ mid- and far- infrared$
named for their relation to the isible spectrum. The far-infrared$ (appro#. >- cm-) lying adPacent to themicro"ae region$ has lo" energy and may be used for rotational spectroscopy. The mid- infrared (appro#. >-> cm-) may be used to study the fundamental ibrations
and associated rotational-ibrational structure$ "hilst thehigher energy near-I (>-> cm-) can e#cite oertoneor harmonic ibrations.
Infrared spectroscopy "orks because chemical bondshae specific freuencies at "hich they ibrate correspondingto energy leels. The resonant freuencies or (irationalfreuencie! are determined by the shape of the molecular potential energy surfaces$ the masses of the atoms and$
eentually by the associated ibronic coupling. In order for aibrational mode in a molecule to be I actie$ it must beassociated "ith changes in the permanent dipole. Inparticular$ in the *orn-/ppenheimer and harmonicappro#imations$ i.e. "hen the molecular 7amiltoniancorresponding to the electronic ground state can beappro#imated by a harmonic oscillator in the neighborhood of the euilibrium molecular geometry$ the resonant freuencies
are determined by the normal modes corresponding to themolecular electronic ground state potential energy surface.0eertheless$ the resonant freuencies can be in a firstapproach related to the strength of the bond$ and the mass of the atoms at either end of it. Thus$ the freuency of theibrations can be associated "ith a particular bond type.
!imple diatomic molecules hae only one bond$ "hich
may stretch. More comple# molecules may hae many bonds$and ibrations can be conPugated$ leading to infraredabsorptions at characteristic freuencies that may be relatedto chemical groups. The atoms in a 57= group$ commonlyfound in organic compounds can ibrate in si# different "ays$!)etrical an$ a!)etrical !tretching$ !ci!!oring$roc6ing$ /agging and t/i!ting.
A beam of infra-red light is produced and split into t"oseparate beams. /ne is passed through the sample$ theother passed through a reference "hich is often thesubstance the sample is dissoled in. The beams are bothreflected back to"ards a detector (6ig. .=)$ ho"eer firstthey pass through a splitter "hich uickly alternates "hich of the t"o beams enters the detector. The t"o signals are thencompared and a printout is obtained.
A reference is used for t"o reasons+
• This preents fluctuations in the output of the sourceaffecting the data
• This allo"s the effects of the solent to be cancelledout (the reference is usually a pure form of the solentthe sample is in)
Atomic spectroscopy includes both 6lame Emission and Atomic Absorption spectroscopy. 6lame Emission or 6ame photometry
refers to the measurement of the radiations emitted by certainelements "hen e#posed to high temperature of a flame. Atomsof such elements absorb energy from heat and thus becomee#cited$ i.e. an outer electron shift to a high energy leel. Atomsin their e#cited state are unstable. Therefore on cooling theelectron falls back to the lo"er energy leel$ and atomsreturned to their original stable form$ kno"n as the groundstate. Buring this process the atoms emit the absorbed energy
in the form of radiations. This is kno"n as atomic emission. Thetype of radiation emitted or the "aelength of the emittedradiation is referred to as Demission spectra. Each element hascharacteristic emission spectra$ "hich aids in the identificationof elements. !ince the intensity of the emitted radiation isproportional to the number of atoms of the element in a giensample$ this techniue is also useful for uantitatie analysis.The instrument used for this purpose is kno"n as flame
photometer.
In atomic absorption spectroscopy$ the "aelength andintensity of the radiation absorbed by the atoms are measuredrather than the emission. !o AA! is an improed techniue$
used for routine analysis of different mineral elements. ikeemission spectra$ each element has a characteristic absorptionspectra$ "hich can be used for both ualitatie and uantitatieanalysis. In both atomic emission and absorption spectroscopythe sample solution is aspirated into a flame$ "here it isapori,ed and atomi,ed (broken into atoms). The atoms thenabsorbed or emit the energy.
NST#MENT"TON
Atomic Absorption spectrophotometer consistsessentially of the follo"ing parts
• adiation source (7ollo" cathode amp)• 5ell (*urner 1 0ebuli,er)• 5hopper (otatory sector 2heel)• Betector (&hotomultifier tube)• Meter read-out system
0uclear magnetic resonance (0M) spectroscopy deals "iththe behaior of atomic nucleons in magnetic fields. Mostnuclei$ including the proton and the electron$ possessinherent magnetic fields. In the presence of another (e#ternal)intense magnetic field$ the nuclei absorb energy(electromagnetic radiation) and can assume specific
orientations "ith corresponding potential energy leels.Techniues hae been inented to detect the minute amountof energy absorbed or emitted as the nuclei Pump from oneenergy leel to another. This is the basis of nuclear magneticresonance (0M). It has been used for the last ? years as areliable and sensitie method for determining the structure of biomolecules.
The high resolution 0M of homogenous solutionsproides information about+
• 6unctional group analysis (chemical shifts)• *onding connectiity and orientation (L coupling)• Through space connectiity.• Molecular conformations$ B0A$ peptide and
The nuclei of all elements carry a charge. 2hen thespins of the protons and neutrons comprising these nuclei are
not paired (i.e. the nuclei possess an odd number of protons$an odd number of neutrons$ or both) the oerall spin of thecharged nucleus generates a magnetic dipole along the spina#is$ and the intrinsic magnitude of this dipole is afundamental nuclear property called$ the nuclear magneticmoment. It aries "ith each element. The s
charge distribution in the nucleons is a function of its internalstructure and if this is spherical (i.e. analogous to thesymmetry of a I! hydrogen orbital)$ it is said to hae acorresponding spin momentum number of K . E#amples of such nuclei are 7$ <5$ ?0$ H6 and <&$ etc.
T"o /rientation of the 0ucleusa. against the magnetic field ( high energy)b. parallel to the magnetic field ( lo" energy)
If the oriented nuclei are no" irradiated "ithelectromagnetic radiation of the proper freuency$ the lo"er
energy state "ill absorb a uantum of energy and spin-flip tothe high energy state. 2hen this spin transition occurs$ thenuclei are said to be in resonance "ith the applied radiation$hence named nuclear magnetic resonance.
The 0M signal for a gien nuclei is referred to as thecheical!hift$ and$ in general$ protons or carbons adPacentto electronegatie atoms "ill be deshielded and moed to a
higher chemical shift (undergo transition at a lo"er appliedfield). The scale utili,ed for measuring chemical shifts isdefined by the euation sho"n belo"+
5hemical shift () K (shift obseredoscillator freuency) # @
ppm.The factor of @ is introduced into the euation to gie asimple "hole number scale for conenience.
E#perimentally$ for both 7 and <58 0M$ the !caleis anchored at ,ero by the 0M absorption of the moleculetetramethyl silane ((57<)>!i) in "hich the carbons and protonsare more highly shielded than those obsered in mostcommon organic molecules$ 6or 7 0M$ the scale
generally e#tend from -= ppm3 the scale for<
5 nuclei$ho"eer$ is much larger and coers the range -== ppm.
/n the scale for 7 for 0M simple hydrocarbonprotons tend to absorb in the region .?-.?$ protons on acarbon adPacent to a carbonyl are shifted to =$electronegatie atoms (o#ygen or halogens) moe j-protonsto <->$ alkene protons are shifted to ?-@$ aromatic
protons to -C$ aldehydic protons to $ and the mosthighly shifted protons are generally those of carbo#ylic acids$"ith alues of =.
6or <5 0M$ simple methyl carbons tend to absorb inthe region =-@?$ electronegatie atoms (o#ygen or halogens) moe attached to >-C$ alkyne carbons areshifted to -H$ alkene carbons to -?$ aromatic
carbons to =-$ and most highly shifted carbons aregenerally those of carbonyls$ "ith alues of C-==.
6or a molecule such as diethyl ether$57<57=/57=57<$ t"o types of protons "ould be predicted toappear in the 0M spectrum3 a simple 57< in the area of K$ and a 57= shifted do"n to about jK > by theelectronegatie o#ygen. The 0M spectrum of diethyl ether$
6ig =.= 0M spectrum of diethyl ether This multiplicity is due to the phenomena kno"n asspin coupling and arises because of interaction of the protonmagnetic field "ith bonding electrons. In essence$ eachproton can hae one of t"o possible spin orientations in theapplied field$ so that the magnetic field sensed by adPacentprotons can hae one of t"o possible alues. The result isthat n protons "ill split adPacent protons into (n ) peaks.
The intensities of these peaks are simply a result of thepossible spin orientations$ thus$ the protons of a 57= groupcan hae the follo"ing possible spins+
The middle pair is degenerated therefore a protonadPacent to a 57= group "ill be spited into three separate
peaks in the ratio +=+.
The separation bet"een these peaks is referred to asthe coupling constant L$ "hich is measured in 7,3 typicalalues for L seldom e#ceed = 7, and it is important to notethat sets of coupled protons "ill display e#actly the samecoupling constant.
An 0.M.. spectrometer contains a massie andintricate collection of electronics of "hich "e can consider only the basic elements. 2e must remember that "e aredealing "ith intense magnetic fields reuiring enormous$precisely controlled po"er supplies$ and precisely controlledfreuencies. 'nfortunately$ most of the kilo"atts reuired bythe instruments are dissipated as heat and the fe" micro"attsof signals that "e obtained from the sample must be amplifiedby another intricate electronic system. The comple#ity of
operation of the instrument represent a barrier to its "idespread use$ but een so it is rapidly becoming nearlyaailable as an infrared spectrometer. The basic componentsof a typical 0M spectrometer are gien as under in (6igure=.>)+
• Magnet: "ith a strong$ stable$ homogeneous field.The field must be constant oer the area of the
sample and oer the period of time of the e#periment.• " !/eep generator: "hich supplies a ariable B-5
current to a secondary magnet so that the totalapplied magnetic field can be aried (s"ept) oer alimited range.
(transmitter) connected to a coil "hich transmitsenergy to the sample in direction perpendicular to themagnetic field.
• " rea$out !)!te: consisting of an amplifier$recorder$ and possible additional components for increased sensitiity$ accuracy$ or conenience.
• " !aple container: usually a glass tube spun by anair-drien turbine to aerage the magnetic field oer the sample dimensions.
!chematic diagram of 0.M.. !pectrometer
M"SS SPECT#OSCOPF 'MS*
The mass spectroscopy (M!) sort out charged gasmolecules (ions) according to their masses. It is the mostuseful techniue to determine structures of comple# organic
molecules. It is ery sensitie analytical tool that can detect. ^g or less of material. It is also uniue in that for the greatmaPority of compounds it directly determines the molecular "eight of the sample. In addition$ it also detects functionalgroups$ hetero-atoms and their arrangement in the molecule.
The sensitiity of the instrument plus the usefulness of datamake it an ideal unit for coupling "ith a gas chromatograph or a high performance liuid chromatograph (G5-M! and 5-M!). This coupling results in a po"erful tool for theuantitatie and ualitatie analysis of comple# compounds.Material separated by thin layer chromatography (T5)$ paper or column chromatography$ etc. may also be analy,ed by themass spectrometer.
P#NCPLE
The mass spectroscopy (M!) is based upon theprinciple that the sample is first ioni,ed by bombardment "ithstream of electrons from a hot filament$ a process kno"n aselectron impact (EI) ioni,ation. The positiely charged ions soformed are then separated according to their mass to chargeratio. Bispersion of ions occurs through deflection by electric
and magnetic fields. After separation$ the ions enter adetector and then on to an amplifier to boost signal. The ionsare identified from their masses and their intensity ismeasured from their corresponding electrical signal.5omputing integrating unit records all the data and conertsthe electrical impulses into isual display$ a hard copy of "hich can also be prepared. The computer also dries themass spectrometer.
!ince each compound has a uniue fragmentationpattern$ so compounds can be easily identified from their kno"n ion fragments. Many compounds$ e.g. fatty acids$sterols and pesticides hae been accurately identified by G5-M!.
A typical mass spectrometer consists of fie basic units
(i) "n inlet !)!te: To introduce the sample$ "hichin first heated to apori,e it3 the apor is thenallo"ed to diffuse into the electron source unit.
(ii) "n electron !ource unit,chaer: To produce abeam of electrons to ioni,e the sample. 'sually a -%electron beam is applied. This is energetic enough to
break any bonds likely to be present "ithin the
sample.(iii) "n anal)+er region: To separate ions according totheir mass to charge ratio by electric and magnetic fields.The uadruple mass analy,er (or filter) is commonlyused. It consists of four parallel rods$ on "hich are
impressed a specific radio freuency and ariable B5oltage.(i) " collector an$ recor$ing !)!te: To detect the
ions and measures their intensity() " (acuu !)!te: To maintain high acuum in theinstrument for normal functioning.
2hen an organic compound haing lo" ioni,ationpotential is bombarded "ith an electron beam$ the initial resultis formation of a molecular ion carrying a positie charge. It isformed by the remoal of one electron from the samplemolecule leaing a positie charge on it. 7ence it is calledmolecular ion or parent ion. This ion denoted by M is aradical ion "hich is usually formed "ith sufficient e#cess
energy so that some or many fragment ions are also formeddue to the breakage of bonds "ithin the molecule. Eachcompound yield characteristic molecular ion (M) andfragment ions$ "hich are useful to identify the compound andelucidate its structure. The series of fragment ions of acompound is called its fragmentation pattern or crackingpatternmass spectrum.
The mass spectrum consist of a series of peaks of arious amplitude$ each peak is recorded as alue of massdiided by charge (M9). !ince "e deal "ith singly chargedions (i.e. 9K) such a alue is the mass (m) of the ioncorresponding that peak. &eak heights are proportional to thenumber of ions of each mass. The galanometer records aslight ion current at each mass unit.
The first step in making use of the data is to assign
M9 alues to the arious peaks. This is generally done byreferring the spectra to that of calibration compounds of kno"n M9 alues. After assigning of mass numbers$ theintensities of arious peaks are tabulated. The intensities aregenerally e#pressed as percentage of the most intense peakin the spectrum called the basepeak In most cases the base
