Topic 10Organic Chemistry
IB Core Objective
• 10.1.1 Describe the features of a homologous series.
10.1.1 Describe the features of a homologous series.
• Carbon atoms can form long chains.• These chains can also contain functional groups:
which are other atoms such as oxygen, nitrogen or halogens.
• Some chains may have the same functional group, but only differ by the presence of additional carbon atoms and associated hydrogen atoms.
• These series of compounds that are related are called homologous series.
10.1.1 Describe the features of a homologous series.
Homologous Series• Differ from each other by a CH2 unit.• Can be represented by a general formula
(example: alkanes is CnH2n+2)• Compounds have similar chemical properties.• As the number of carbon atoms present
increases, the physical properties will vary in a regular manner.
10.1.1 Describe the features of a homologous series.
Alkanes Alkanes are an example of a homologous
series. Alkanes have the general formula CnH2n+2
So when using this formula, what kind of bond (single, double, triple) would form between two or more carbons?
A: Single
10.1.1 Describe the features of a homologous series.
Molecular models1. Build a methane (CH4) model.2. In homologous series, successive compounds
differ by a CH2 unit. Build a CH2 unit, and join it with your methane.
3. What kind of C-C bond does your new molecule have? What would the molecular formula be? Does it follow the CnH2n+2 formula?
IB Core Objective
• 10.1.2 Predict and explain the trends in boiling points of members of a homologous series.
10.1.2 Predict and explain the trends in boiling points of members of a homologous series.
• First, lets review van der Waals’ forces. • They are weak forces that attract molecules to
each other.• This is caused by random fluctuations in the
electron clouds, where they can temporarily produce dipoles.
When the overall mass increases, so does the strength of the van der Waals’ forces.
10.1.2 Predict and explain the trends in boiling points of members of a homologous series.
What would happen to the forces of attraction between molecules when the number of carbons in the chain (CH2) are increased?
A: The forces of attraction would increase.What happens to the boiling point when forces
of attraction increase?A: Boiling point increases as well.
10.1.2 Predict and explain the trends in boiling points of members of a homologous series.
IB Core Objective
• 10.1.3 Distinguish between empirical, molecular and structural formulas.
10.1.3 Distinguish between empirical, molecular and structural formulas.
• Structural • Molecular • Empirical
H
C
H
H
H
H
HH
C CC
O
C
HH
O
H
Pentanoic Acid
CH3(CH2)3COOH
Condensed structural formula
What is the Molecular and empirical formula?
Writing structures
• ‘R’ is sometimes used to represent the carbon chain. – ROH represents the functional group alcohol
attached to some carbon chain.
• Rings: Benzene Ring(Alternating double
bonds)
IB Core Objective
• 10.1.4 Describe structural isomers as compounds with the same molecular formula but with different arrangements of atoms.
10.1.4 Describe structural isomers as compounds with the same molecular formula but with different arrangements of atoms.
• Totally different compounds with the same molecular formula– This includes a unique MP and BP– May have totally different chemical properties
Isomers
Structural(Different Bonding)
Stereo(Different shape)
Structural Isomers
OH
OH
Propanol Primary alcohol
MP -127 oC
Iso-propanol or 2-PropanolSecondary alcohol
MP -88oC
Make a molecular model of both. What
is the molecular formula?
C3H7OH
IB Core Objectives
• 10.1.5 Deduce structural formulas for the isomers of the non-cyclic alkanes up to C6.
• 10.1.6 Apply IUPAC rules for naming the isomers of the non-cyclic alkanes up to C6.
10.1.5 Deduce structural formulas for the isomers of the non-cyclic alkanes up to C6.
10.1.6 Apply IUPAC rules for naming the isomers of the non-cyclic alkanes up to C6.
Mice Eat Peanut Butter!Or….
Methane, Ethane, Propane, ButaneThe first four alkanes!
Alkanes• Prefix: Indicates the
longest carbon chain. • Ex. Meth - 1 carbon• Eth - 2 • Prop - 3• But - 4• Pent - 5 • Hex - 6• Hept- 7• Oct- 8• Non - 9• Dec- 10
Hydrogen atoms are
removed for clarity
Alkanes• Suffix: The ending portion of the name.
• All carbon based organic compounds that contain only single bonds have the ending –ane
Methane CH4
Ethane CH3CH3
Propane CH3CH2CH3
Butane CH3CH2CH2CH3
Pentane CH3CH2CH2CH2CH3
Hexane CH3CH2CH2CH2CH2CH3
Substituents/ Functional groups
• 1st number the carbon chain. In this case no matter which way you go it is a 5 carbon chain, hence pentane.
• Next the subgroup must be named, in this case it is a methyl group off of the 4th carbon. BUT the main chain must be numbered closest to the sub group...so you must re-number if you didn’t do it this way.
• Name: 2-Methylpentane
2
31 4
5
4
3
Methyl
5 2
1
-CH3 = 1 carbon= meth=Methyl
(functional group)
Carbon sub chains have the
suffix -yl
Multiple Substiuent/Functional Groups
• In this case there are 2 methyl groups on the same carbon.
• Name: 2,2-Dimethylpentane
4
3
Methyl
5 21
Methyl
1 –mono2 –di3 –tri4 –tetra5 –pent6 –hex7 –hept8 –oct9 –non10 -dec
di- is used because it indicates 2 of the same
functional groups
Multiple Functional Groups
• In this case you list the sub groups in alphabetical order first.
• Name: 3-Ethyl-3,4-dimethylhexane
Ethyl4
2
Methyl
53 1
Methyl
6
IB Core Objectives
• 10.1.9 Deduce structural formulas for compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide.
• 10.1.10 Apply IUPAC rules for naming compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide.
Functional Groups to Know
• -OH (alcohol)
• R-CHO (aldehyde)
• R-COR (Ketone)
• R-COOH (carboxylic acid)
• -X (halide)
H
H
C
H
HO
Simplified structure
H
C
O
RC
O
R RC
O
R O HH
H
C
H
Cl
ALCOHOLS
If a hydrogen atom of an alkane is replaced by an —OH group, the compound is called an Alcohol.
Alcohols derived from ALKANES are called ALKANOLS.
A functional group is a small set of atoms, held together by covalent bonds in a specific, characteristic arrangement that is responsible for the principal physical and chemical properties of an organic compound.
We interrupt this objective to bring you an all new objective!!
IB Core Objective
• 10.1.12 Identify primary, secondary and tertiary carbon atoms in alcohols and halogenoalkanes.
Three CLASSES of alcohols occur according to the position of the HYDROXYL, OH, group. The classes of alkanols are:• PRIMARY • SECONDARY• TERTIARY
PRIMARY ALCOHOLSR–CH2– OH and HCH2–OH
R— C—OH
H
H
—C—OH
H
H
H
MethanolCH3OH
General formula
PRIMARY ALCOHOLS (cont.)Structural formula for Ethanol (Ethyl Alcohol) :
OHH–C–H
H
C–H
H
H–C–H
H
C–H
H
C–H
H
C–H
HOH
1-butanol: 2-methyl-1-butanol:
–C —H
H C —H
C—H
H
C–H
H
1 2 3 4H
H–C–H
H
HO
SECONDARY ALCOHOLS
R2CH—OH —C—OH
H
R´
R
2-propanol
H—C—
H
H
C—
H
OH
C—H
H
H
3-methyl-2-butanol
H—C —
H
H
C —
H
C—
H
C—H
H
HOH
H–C–H
H
1234
C3H7OH C5H11OH
TERTIARY ALCOHOLS
R3COH
2-methyl-2-propanol
H—C —
H
H
C —
H–C–H
H
OH
C—H
H
H
C4H9OH
21 3
R´´
R´
R – C – OH
ISOMERS of C4H10O
H–C–H
H
C–H
H
C–H
H
C–H
HOH
H–C–H
H
C–H
H
C–H
O
C–H
HH
H
H
C–H–C–
H
H
–CH
CH H
HOH
HPRIMARY
ALCOHOLS
SECONDARY
ALCOHOLTERTIARY
ALCOHOL
–C–H–C–
H
HC–O
H
H
H
HC–H
H
H
ETHER
H–C–H
H
C–H
H
C–H
O
C–H
HH
H
H—C —
H
H
C —
H–C–H
H
O
C—H
H
H
H
10.1.12 Identify primary, secondary and tertiary carbon atoms in alcohols and halogenoalkanes.
Objectives 10.1.9, 10.1.10
Halogenoalkanes
An alkane with a halogen (fluorine, chlorine, bromine, or iodine).Often represented by an X, or can include the actual halogen (F, Cl, Br, I)
Prefix begins with fluoro-, chloro-, bromo-, or iodo-
Example: Name?CH3 CH CH CH3
Br Cl
A: 2-bromo-3-chlorobutane
10.1.12 Identify primary, secondary and tertiary carbon atoms in alcohols and halogenoalkanes.
• Primary, secondary and tertiary structures are the same for halgeonoalkanes as alcohols.
Describe the difference between primary, secondary and tertiary structures of halgonoalkanes:
• Primary: Carbon the halogen is bonded to is bonded to only one other carbon.
• Secondary: Carbon the halogen is bonded to is bonded to two other carbons.
• Tertiary: Carbon the halogen is bonded to is bonded to three other carbons.
Back to our original objectives
• 10.1.9 Deduce structural formulas for compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide.
• 10.1.10 Apply IUPAC rules for naming compounds containing up to six carbon atoms with one of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid and halide.
ALDEHYDESAldehydes have the suffix –al.
ALKANALSare produced by the
OXIDATION
OF PRIMARY ALCOHOLS (Primary alkanols)
RCH2OH RCHO
R—C—
H
H
OH R—C
H
O
KETONESALKANONES
are produced by the
OXIDATION
OF SECONDARY ALCOHOLS (Secondary alkanols)
R2CHOH R2CO
R—C—
H
R´
OHR— C
O
R´
CARBOXYLIC ACIDS
R — C
O
O–H
ALDEHYDES are OXIDISED to CARBOXYLIC ACIDS
MnO4¯(aq)
H+H3C — C
O
H
H3C— C
O
O H
Ethanal Ethanoic acid(Acetic acid)
– +
Aldehyde functional group
Carboxyl functional group
IB Core Objectives
• 10.1.7 Deduce structural formulas for the isomers of the straight-chain alkenes up to C6.
• 10.1.8 Apply IUPAC rules for naming the isomers of the straight-chain alkenes up to C6.
10.1.7 Deduce structural formulas for the isomers of the straight-chain alkenes up to C6. 10.1.8 Apply IUPAC rules for naming the isomers of the straight-chain alkenes up to C6.
Alkenes• General formula: CnH2n
• If there are double bonds involved the suffix changes from –ane to –ene.– Molecules are considered un-saturated if
there are double bonds present.
• After naming the longest chain, number the carbons closest to the double bond
Alkenes
• Location of the double bond is important, anything greater than 3 carbons must include a location–Prefix – location – suffix–Pent-1-ene
CH2CH
CH2CH2
CH3
IB Core Objective
• 10.1.11 Identify the following functional groups when present in structural formulas: amino (NH2), benzene ring ( ) and esters (RCOOR).
AMINES
Amines are organic compounds derived from ammonia, NH3.
One or more of the hydrogen atoms are replaced by alkyl groups.
Like alcohols, there can be primary, secondary and tertiary amines.
ammonia
Primary Amine
Secondary AmineTertiary Amine
N
H
H
H
N
R
H
H
N
R
R´
H
N
R
R´
R´´
Amines
methyl amineCH3
N
H
H
dimethyl amine CH3
CH3
N H
primary
secondary
CH3NH2
(CH3)2NH
BenzeneCH
CH
CH
CH
CH
CH
Six sided ring with alternating double bondsCompounds with benzene are often called aromatic.It is highly flammable with a sweet smell.
OH
Phenol
NH2
Phenylamine
Review of Functional Groups
• Alcohol: R-OH (-ol)• Halide: R-X (F, Cl, Br, I)• Ketone: R-CO-R or R2CO• Aldehydes: R-CHO• Benzene: C6H6
• Carboxyl: R-COOH
OH
Propan-1-ol1-
chloropropane
ClO
ButanonePropanal
O
H
Benzene
O
HO
Propanoic acid
ESTERS
Carboxylic Acid ESTER + Water
R — C
O
O
+OHR´–
Alcohol +
–H – R´R — C
O
O
+OHH–
Alcohol Carboxylic Acid ESTER Water
R-COO-R´
-oate-ol -oic
OHCH3 - +
CH3 –
MethanolEthanoic Acid
O
OC
H
O
CH3 –
O
OC
- CH3
methyl ethanoate
+OHH–
Water
Ester functional group
(methyl alcohol)
Esters
Esters have strong sweet smells which are often floral or fruity.
Ester Fragrance ethyl methanoate 3-methylbutyl ethanoate ethyl 2-methylbutanoate phenylmethyl ethanoate
raspberries pears apples jasmine
IB Core Objective
• 10.1.13 Discuss the volatility and solubility in water of compounds containing the functional groups listed in 10.1.9.
• Those functional groups are alcohol, aldehyde, ketone, carboxylic acid, and halide.
10.1.13 Discuss the volatility and solubility in water of compounds containing the functional groups listed in 10.1.9.
• Aldehydes, ketones, and halogens will give the molecule more polarity, which results in dipole-dipole forces. What would happen to the melting and boiling point when these functional groups are added?
• A: They would be higher.• Alcohol and carboxylic acid give rise to hydrogen bonding.
Would the melting points and boiling points be higher or lower than the aldehydes, ketones and halogens?
• A: They would be higher.• What about solubility?• Like dissolves like. More polar, more likely they will dissolve
in water.
IB Core Objective
• 10.2.1 Explain the low reactivity of alkanes in terms of bond enthalpies and bond polarities.
10.2.1 Explain the low reactivity of alkanes in terms of bond enthalpies and bond polarities.
• Chemically, alkanes are very unreactive.• Weird, when you think that most alkanes are used
for quick burning (propane, butane, etc.)• We use alkanes to store reactive metals such as
sodium.• Because alkanes have strong carbon to carbon and
carbon to hydrogen bonds, they require a high activation energy.
• When this activation energy is provided, the reaction is highly exothermic.
IB Core Objective
• 10.2.2 Describe, using equations, the complete and incomplete combustion of alkanes
10.2.2 Describe, using equations, the complete and incomplete combustion of alkanes
• Complete Combustion (Excess Oxygen)____C8H18 + ____O2 ____CO2 + ____H2O
• Incomplete Combustion (Limited Oxygen)C8H18 + O2 CO2 + CO + C + H2O
Evidence of Incomplete Combustion: Black soot or yellow/orange flame. ... Chim
chiminey.. Chim chiminey.. Chim Chim cher-oo
Why where chimney sweep so important in the early 1900’s?
10.2.3 Describe, using equations, the reactions of methane and ethane with chlorine and bromine.
10.2.4 Explain the reactions of methane and ethane with chlorine and bromine in terms of free-radical mechanism.
Substitution Reactions (10.2.3)
• One atom is kicked off by another more reactive group.
H
CH
H
C
H
H
H
Cl Cl
Cl
Cl
Un-bonded e- move directly to H to form
a new bond
H
Cl
1-Chloroethane
Substitution • With more available chlorine, the reaction will
continue to produce a mix of products.
CH
H
C H
Cl H
Cl
1,1-Dichloroethane
H C
H
C H
H
Cl Cl
1,2-Dichloroethane
C
C
Cl
Cl
Cl
Cl
Cl
Cl
hexachloroethaneWith large excess of Chlorine
Free Radical Substitution
• Radicals: Highly reactive molecules possessing a singly unpaired electron.
• There are three major steps:– Initiation– Propagation– Termination
Initiation
• Light is used to temporarily break the bond between either Bromine or Chlorine to form the free radical.
Cl ClCl Cl
Ya, well im taking my electron and going
home
Fine!! I`m taking mine then too!
Hey Ma!! I`m a free radical now!!!
Oh great!!! He`s so unstable when
he`s like this!!
Propagation
H
H
C
H
H
• Two possibilities:– 1) Cl radical reacts with an alkane– 2) Radical alkane reacts with Cl2(g)
Cl
C
H
H
H
H
H
C
H
Cl Cl
Termination• Three possibilities:– 1) Cl radical reacts with another Cl radical – 2) Cl radical reacts with an alkane radical– 3) Alkane radical react with another alkane radical
Cl ClCl Cl
Your electron or your life mate!
Just about to ask you the same thing!!
Let`s Do This!!!!
Bring it!!Ahhhhhhhhh!!!
Tired yet?NOPE!
Sigh...Guess we`ll be hanging out together for a
while eh?
Termination• Three possibilities:– 1) Cl radical reacts with another Cl radical – 2) Cl radical reacts with an alkane radical– 3) Alkane radical react with another alkane radical
C
H
H
H
C
H
H
H
Cl
C
H
H
H
C
H
H
H
Cl
C
H
H
H
C
H
H
H
Cl Cl
IB Core Objective
• 10.3.1 Describe, using equations, the reactions of alkenes with hydrogen and halogens.
10.3.1 Describe, using equations, the reactions of alkenes with hydrogen and halogens.
Addition reactionReaction in which double bond of alkene is
converted to a single bond. Two new bonds are formed with the molecule it reacted with.
When hydrogen reacts with an alkene and a nickel catalyst:
CH2 CH2 + H2 CH2 CH2
H HNi
10.3.1 Describe, using equations, the reactions of alkenes with hydrogen and halogens.
• Alkenes are unsaturated, because they can undergo addition reactions across the double bond.
• Alkanes are saturated, because no more addition reactions can occur!
Mmmm, no more addition
reactions…I like the sound of that
Hydrogenation• This reaction requires more energy and a heated
platinum, nickel or palladium catalyst is needed for hydrogenation of the unsaturated bond.– Decreasing the number of unsaturated bonds will cause an
increase in the MP.
– Margarine is made from oils, by saturating some of the double bonds causing the liquid to become solid at room temp.
C
H
C
H
H
H
H
C
H H
H
10.3.1 Describe, using equations, the reactions of alkenes with hydrogen and halogens.
• Bromination: • Alkanes and alkenes can be determined by
bromination. The orange bromine will disappear if there are double bonds present.
C
H
C
H
H
H
H
C
Br Br
H
Note: This reaction also takes place spontaneously at room temperature with
chlorine and iodine
IB Core Objective
• 10.3.2 Describe, using equations, the reactions of symmetrical alkenes with hydrogen halides and water.
10.3.2 Describe, using equations, the reactions of symmetrical alkenes with hydrogen halides and water.
• Symmetrical: If you cut the molecule in half right across the double bond, both sides would look the same (mirror images).
10.3.2 Describe, using equations, the reactions of symmetrical alkenes with hydrogen halides and water.
• A spontaneous reaction can occur with a hydrogen halide (HCl) and an alkene:
CH2 CH2 + ClH CH2CH2
H Cl
10.3.2 Describe, using equations, the reactions of symmetrical alkenes with hydrogen halides and water.
Reaction of Alkene with Water
What do you notice about the arrows?At a temperature of 300°C, and high pressure
(7atm), the equilibrium is driven to the right.Or H2SO4 could be used as a catalyst.This process is used to create ethanol.
CH2 CH2
OHHCH2 CH2 + OH2
IB Core Objective
• 10.3.3 Distinguish between alkanes and alkenes using bromine water.
• We learned about bromination previously.• We will be using bromine water to test for
alkenes in an experiment on Sunday, January 31st.
IB Core Objective
• 10.3.4 Outline the polymerization of alkenes.
• Polymers: long chain molecules formed by joining together of monomers.
• Need to know formation of polyethene, polychloroethene, and polypropene.
• Need to identify the repeating unit. • Example –(CH2-CH2-)n- for polyethene.
10.3.4 Outline the polymerization of alkenes.
• Polyethene, also known as polyethylene, is used for the manufacturing of plastics.
• Use ethene monomers to form polyethene polymers.
Addition Polymerization for Polyethene• Poly = many and Mer = Unit• Will continue adding from both ends until there are no
longer any ethene molecules available – Could potentially add to the other end too
H
H
C
H
H
C
H
H H
H
CC Radicals have formed and are highly reactive
H
H
C
H
H
C
H
C
H
H
HH
C CC C
HH H
H
H
H H
H
CC
H
H H
HCC
H
10.3.4 Outline the polymerization of alkenes.
Poly(chloroethene)• Better known as PVC (PolyVinyl Chloride)• Used in pipes, siding, clothing, upholstery, and
inflatable toys/products.
10.3.4 Outline the polymerization of alkenes.
Poly(chloroethene)• Formed by polymerisation of chloroethene.• Repeating unit is [-CH2-CHCl-]n
• Chloroethene monomer
• Polymerisation:
C CCl
H
H
H
C C C C CH H H
H H H H H
Cl Cl
10.3.4 Outline the polymerization of alkenes.
Polypropene• Also known as polypropylene.• Used in manufacture of packaging, ropes,
plastic parts, and laboratory equipment.• Formed by propene monomers:
• Polypropene polymer:C C C C CH H H
H H H H H
CH3 CH3
C CCH3
H
H
H
IB Core Objective
• 10.3.5 Outline the economic importance of the reactions of alkenes.
We have already reviewed:• The hydrogenation of vegetable oils to make
margarine.• The hydration of ethene to manufacture
ethanol.• Polymerization to manufacture plastics.
IB Core Objective
• 10.5.1 Describe, using equations, the substitution reactions of halogenoalkanes with sodium hydroxide.
• 10.5.2 Explain the substitution reactions of halogenoalkanes with sodium hydroxide in terms of SN1 and SN2 mechanisms.
Objectives 10.5.1 and 10.5.2
• Fluorocarbons are extremely unreactive because the carbon-fluorine bond is so strong.
• Bromochlorodifluoromethane (commonly called Halon 1211) is used for extinguishing electrical fires and aircraft fires.
C C FH
HH
H
H
ATTACK OF THE NUCLEOPHILES
A long time ago---in a lab far, farAway, molecules began mixing.Little did some of the molecules knowThat there was a positive pole beingExposed to the dark side.These molecules knew they were Vulnerable to a great evil lead byDarth Hydroxide. The future of the Halogenoalkane forces lay in the handsOf Princess Halogen. However, the Attack of the nucleophiles could beToo great……
Objectives 10.5.1 and 10.5.2
• Because halogens are more electronegative than carbon, the carbon has a slight positive charge.
• This positive charge makes it susceptible to attack by the nucleophiles.
+ Nucleophile
-
Objectives 10.5.1 and 10.5.2
• An example of a nucleophilic substitution is bromoethane with hydroxide ion.
ethanolCH3CH2Br + OH-(aq) CH3CH2OH + Br-
The nucleophile attacks and docks, while Princess
Halogen escapes
Objectives 10.5.1 and 10.5.2
• There are two mechanisms of substitution, SN1, or SN2.
• SN1 : One stands for unimolecular.– 1) Leaving group leaves taking an electron (slow, rate determining
step)
– 2) Carbocation is formed (Positively charged) • Intermediate step
– 3) Nucleophile donates electrons and forms new bond
• HL Understanding: Enantiomers– Products are a racemic mixture. A 50:50 product of right hand and
left hand rotation.
SN1 Substitution
ClC
H
H
H
δ+ δ––
R
–R
OH H C
–
OH
C
R
H
R
Attack of the nucleophile!
Princess Halogen escapes before the nucleophile
attacks!
Objectives 10.5.1 and 10.5.2
• SN2 : An ‘attack from the rear’ substitution reaction – 1) Nucleophile attaches to the opposite side of the leaving
group.
– 2) Both are attached at the same time, hence the 2 because it is bimolecular.
– 3) Leaving group leaves and substitution is complete
• HL Objective: Enantiomers and Polarimetry– The product has the opposite rotation of the starting
material.
SN2 Substitution
Clδ+ δ––
H
– –
H
H COH
The nucleophile attacks from the
back!!
Princess Halogen realizes after the
nucleophile docks there is no hope!So she leaves…..
Objectives 10.5.1 and 10.5.2
Primary, Secondary, and Tertiary Halogenoalkanes• Tertiary halogenoalkanes proceed via an SN1
mechanism, because it is too bulky to proceed via SN2.
• This “lack of room” for five groups is known as steric hindrance.
Objectives 10.5.1 and 10.5.2
• Primary halogenoalkanes proceed by SN2 mechanism.
• This is because SN1 is unfavorable because the carbon doesn’t like to form carbocations—too much positive charge.
• In tertiary halogenoalkanes the positive charge is spread over more atoms, called the positive inductive effect.
Objectives 10.5.1 and 10.5.2
• Secondary halogenoalkanes can proceed by a mixture of SN1 and SN2.
ReviewWhat is the product for the below reaction, and
by which mechanism does it form?
CCH3
CH3CH3
Br + OH- →
Now, show the intermediate step for this SN1 mechanism
+ -CH3
CH3
BrC
CH3
-OH
Br-
OH- ion with 2-bromo,2-methylpropane (SN1)
2-methylpropan-2-ol
reaction equation
1(species reactingin the slowest step)
SN1
S (substitution)N(nucleophilic)
Br-
CH3
CH3
C
CH3
+ CH3
CH3
OHC
CH3
Using Curly Arrows to show movement of electrons
+ -CH3
H
BrC
H
-OH
CH3
H
OHC
H Br-
hydroxide ion with bromoethane (SN2)
ethanol
reaction equation
2(species reacting in the slowest step)
SN2
S (substitution)N(nucleophilic)
Using Curly Arrows to show movement of electrons