Organic Organic ChemistryChemistry

CE 541CE 541

Basic Concepts from Basic Concepts from Organic ChemistryOrganic Chemistry

ElementsElements

““All organic compounds contain All organic compounds contain CARBON in combination to one or CARBON in combination to one or more elements”more elements”

Properties (compared to Properties (compared to inorganics)inorganics)

usually combustibleusually combustible generally have lower melting and generally have lower melting and

boiling pointsboiling points less soluble in waterless soluble in water existence of isomersexistence of isomers slow reactionsslow reactions have high molecular weighthave high molecular weight most of organic compounds can most of organic compounds can

serve as a food for bacteriaserve as a food for bacteria

Sources of Organic Sources of Organic CompoundsCompounds

Nature: sugars, starch, vegetable Nature: sugars, starch, vegetable oils, animal oilsoils, animal oils

Synthetic: manufacturing processesSynthetic: manufacturing processes Fermentation: Alcohols, anti-Fermentation: Alcohols, anti-

biotics, and acids which are biotics, and acids which are derived by the action of derived by the action of microorganisms upon organic microorganisms upon organic matter.matter.

The Carbon AtomThe Carbon Atom

Why many compounds of carbon?Why many compounds of carbon? carbon atom has four electrons to sharecarbon atom has four electrons to share ability of carbon atoms to link together ability of carbon atoms to link together

in a wide variety of ways:in a wide variety of ways: Continuous Open ChainContinuous Open Chain

C C CC C

Chain with BranchesChain with Branches

In a RingIn a Ring

C C CC C

C

C

Chain or Ring Containing Other ElementsChain or Ring Containing Other Elements

C C CC CO

C C

C

C

CN

The structural formula of organic The structural formula of organic compound may be simplified, for compound may be simplified, for example:example:

Can be written as:Can be written as:

CHCH33-CH-CH22-CH-CH22OHOHOr simply as:Or simply as:

CHCH33CHCH22CHCH22OHOH

C CCH

H

H

H

H

H

H

O H

IsomerismIsomerismIsomers “are compounds that contain Isomers “are compounds that contain the same number of the same atoms in the same number of the same atoms in different arrangements”different arrangements”

ExamplesExamples (1)(1)

C CCH

H

H

H

H

O H

O O

(2)(2)

(3)(3)

(4)(4)

Each of the four compounds has its own Each of the four compounds has its own physical and chemical propertiesphysical and chemical properties

C CCH

H

H

H

H

O H

O

O

C CH

H

H

O H

O

O C

H

H

CH

H

H

O C

H

H O

C OH

HydrocarbonsHydrocarbons““Are organic compounds that contain only Carbon and Are organic compounds that contain only Carbon and Hydrogen elements”. The simplest hydrocarbon is Hydrogen elements”. The simplest hydrocarbon is methane (methane (CHCH44). Methane is composed of four (4) ). Methane is composed of four (4) hydrogen atoms and one carbon atomhydrogen atoms and one carbon atom

Hydrogen has one valence electronHydrogen has one valence electron Carbon has four valence electronCarbon has four valence electron

CHCH44

CondensedCondensed ExpandedExpandedStructuralStructural StructuralStructuralFormulaFormula FormulaFormula

CH

H

H

H

Classification of the Classification of the HydrocarbonHydrocarbon

Hydrocarbons

Aliphatic Hydrocarbon

Aromatic Hydrocarbon

Alkanes Alkenes Alkynes

Aliphatic HydrocarbonsAliphatic Hydrocarbons

Two TypesTwo Types

(1) Saturated(1) Saturated

““Those in which adjacent carbon Those in which adjacent carbon atoms are joined by a single bond”atoms are joined by a single bond”

CH

H

H

C

H

H

C

H

H

H

(2) Unsaturated(2) Unsaturated

““Those in which adjacent carbon Those in which adjacent carbon atoms are joined by more than one atoms are joined by more than one bond (at least two of the carbon bond (at least two of the carbon atoms)”atoms)”

CH

H

H

C C

H

H

HC CH

Alkanes (Saturated)Alkanes (Saturated)

““are also known as paraffins”. Their are also known as paraffins”. Their general molecular formula is:general molecular formula is:

CCnnHH2n+22n+2 (for open chain)(for open chain)

Hexane (6 C and 14 H)Hexane (6 C and 14 H)

CH

H

H

C C

HH

H H

HC

H

H

C

H

H

C

H

H

CCnnHH2n2n (for cycloalkanes) (for cycloalkanes)

Cyclohexane (6 C and 12 H)Cyclohexane (6 C and 12 H)

C

C

C

C C

C

HH

H

HH

H

H H

H

HH

H

The simplest alkane compound is The simplest alkane compound is methane (methane (CHCH44). Methane is:). Methane is:

gasgas highly explosivehighly explosive greenhouse gasgreenhouse gas

The First Ten Continuous-The First Ten Continuous-Chain AlkanesChain Alkanes

Molecular FormulaMolecular FormulaStructural FormulaStructural Formula IUPAC NameIUPAC Namenn

CHCH44 CHCH4 4 MethaneMethane11CC22HH66 CHCH33-CH-CH33 EthaneEthane 22CC33HH88 CHCH33-CH-CH22-CH-CH33 PropanePropane 33CC44HH1010 CHCH33-(CH-(CH22))22-CH-CH33 ButaneButane 44CC55HH1212 CHCH33-(CH-(CH22))33-CH-CH33 PentanePentane 55CC66HH14 14 CHCH33-(CH-(CH22))44-CH-CH33 HexaneHexane 66CC77HH1616 CHCH33-(CH-(CH22))55-CH-CH33 HeptaneHeptane 77CC88HH1818 CHCH33-(CH-(CH22))66-CH-CH33 OctaneOctane

88CC99HH2020 CHCH33-(CH-(CH22))77-CH-CH33 NonaneNonane

99CC1010HH2222 CHCH33-(CH-(CH22))88-CH-CH33 DecaneDecane

1010

Butane has two isomersButane has two isomers

n-butanen-butane

isobutane (2 methylpropane)isobutane (2 methylpropane)

CH

H

H

C C

HH

H H

HC

H

H

CH

H

H

C C

H H

H

H

H

HCH

Pentane has three isomersPentane has three isomers

PentanePentane

isopentane (2-methylbutane)isopentane (2-methylbutane)

Neopentane (2,2-dimethylpropane)Neopentane (2,2-dimethylpropane)

CH

H

H

C C

H H

H

H

H

C

H

H

C

H

H

CH

H

H

C C

H

H

HC

H

H

H

H

HCH

CH

H

H

C C

H

H

H

H

H

HCH

HCH

As the number of carbon atoms in As the number of carbon atoms in alkanes was increased, the number of alkanes was increased, the number of constitutional isomers will also constitutional isomers will also increase:increase:

hexane has 5 isomershexane has 5 isomers heptane has 9 isomersheptane has 9 isomers octane has 18 isomersoctane has 18 isomers nonane has 35 isomersnonane has 35 isomers decane has 75 isomersdecane has 75 isomers

How to draw constitutional isomers? How to draw constitutional isomers? Take hexane (CTake hexane (C66HH1414) as an example ) as an example

(hexane has 5 isomers)(hexane has 5 isomers)Draw a carbon skeleton (no hydrogen atoms) using Draw a carbon skeleton (no hydrogen atoms) using all of carbon in a continuous chain.all of carbon in a continuous chain.

Remove one carbon atom from the end of the chain Remove one carbon atom from the end of the chain and place it on another carbon atom so that the and place it on another carbon atom so that the new skeleton differs from the previous carbon new skeleton differs from the previous carbon skeleton. Repeat this procedure until you exhaust skeleton. Repeat this procedure until you exhaust all possibilities of relocating one carbon atomall possibilities of relocating one carbon atom

C C C C C C

C C C C C

C

C C C C C

C

If carbon atom was place on one of the end If carbon atom was place on one of the end atomsatoms

This is similar to the skeleton shown aboveThis is similar to the skeleton shown above

C C C C C

C

Next, if necessary, remove two carbon Next, if necessary, remove two carbon atoms from the continuous chain skeleton in atoms from the continuous chain skeleton in (1) and relocate them either as single (1) and relocate them either as single carbon atoms or as a two carbon fragment carbon atoms or as a two carbon fragment on other atoms in the chain. Write all on other atoms in the chain. Write all possible different skeletons. Continue this possible different skeletons. Continue this procedure, if needed, for three carbon procedure, if needed, for three carbon atoms, till you have the number of atoms, till you have the number of constitutional isomers as given in the constitutional isomers as given in the problem. Check all skeletons to be sure problem. Check all skeletons to be sure that they are all different.that they are all different.

C C C C

C

C

C C C C

CC

Place hydrogen atoms on the carbon atoms in each skeleton, Place hydrogen atoms on the carbon atoms in each skeleton, remembering that there are four (4) bonds to each carbon remembering that there are four (4) bonds to each carbon atom.atom.

The 5 isomers are:The 5 isomers are:CHCH33-CH-CH22-CH-CH22-CH-CH22-CH-CH22-CH-CH33

CHCH33-CH-CH-CH-CH22-CH-CH22-CH-CH33

CHCH33

CHCH33-CH-CH22-CH-CH-CH-CH22-CH-CH33

CHCH33

CHCH33

CHCH33-C-CH-C-CH22-CH-CH33

CHCH33

CHCH33-CH-CH-CH-CH-CH-CH33

CHCH33 CH CH33

Physical Properties of Physical Properties of Alkanes (Table 5-1)Alkanes (Table 5-1)

colorlesscolorless odorlessodorless quite soluble in water (especially quite soluble in water (especially

those having 5 carbon atoms or more)those having 5 carbon atoms or more) dissolve in many solventsdissolve in many solvents at room temperatureat room temperature

CC11 to C to C55 are gaseous are gaseous

CC66 to C to C1717 are liquids are liquids

CC1818 and above are solids and above are solids

Homologous SeriesHomologous Series

When series of compounds differ by a When series of compounds differ by a common increment (such as CHcommon increment (such as CH22 in in the case of alkanes), the series is the case of alkanes), the series is referred to as being homologous referred to as being homologous series. In such cases, a general series. In such cases, a general formula can be established to express formula can be established to express the compounds (in this case Cthe compounds (in this case CnnHH2n+22n+2))

RadicalsRadicals

When one hydrogen atom is dropped When one hydrogen atom is dropped from the methane- series from the methane- series hydrocarbon, the –ane ending is hydrocarbon, the –ane ending is dropped and a –yl is addeddropped and a –yl is added

MethanMethan CHCH44 CHCH33-- methylmethyl

EthaneEthane CC22HH66 CC22HH55- ethyl- ethyl

NomenclatureNomenclature

First consider the nomenclature of the First consider the nomenclature of the Alkyl groups. Alkyl groups are Alkyl groups. Alkyl groups are derived by removal of one hydrogen derived by removal of one hydrogen atom from an alkane. Alkyl groups atom from an alkane. Alkyl groups are named by replacing the –ane are named by replacing the –ane ending of the alkane (methane) by –yl ending of the alkane (methane) by –yl (methyl) in the case of simpler (methyl) in the case of simpler hydrocarbons.hydrocarbons.

Methane CHMethane CH44 CHCH33- Methyl- Methyl

EthaneEthane CHCH33CHCH33 CHCH33CHCH22- Ethyl- Ethyl

PropanePropane CHCH33CHCH22CHCH33 CHCH33CHCH22CHCH22- Propyl- Propyl

ButaneButane CHCH33CHCH22CHCH22CHCH33 CHCH33CHCH22CHCH22CHCH22- Butyl- Butyl

PentanePentane CHCH33CHCH22CHCH22CHCH22CHCH33 CHCH33CHCH22CHCH22CHCH22CHCH22 - - PentylPentyl

HexaneHexane CHCH33CHCH22CHCH22CHCH22CHCH22CHCH33 CHCH33CHCH22CHCH22CHCH22CHCH22CHCH33- Hexyl- Hexyl

Simple Alkyl Groups and Simple Alkyl Groups and their Namestheir Names

The most common The most common alkyl groupsalkyl groups will will be discussed. be discussed.

Methyl GroupMethyl Group

Methane has Methane has one carbon one carbon and four and four hydrogen hydrogen atoms. The atoms. The methyl group methyl group also has one also has one carbon but carbon but only three only three hydrogens. In hydrogens. In place of the place of the fourth fourth hydrogen, hydrogen, there is a there is a bond to bond to something something else.else.

methyl methyl

HH | |H-C- H-C-  | | H H

Ethyl GroupEthyl Group

Ethane has Ethane has two carbons two carbons and six and six hydrogen hydrogen atoms. If any atoms. If any one of those one of those hydrogens is hydrogens is removed and removed and replaced with replaced with a bond to a bond to something something else, you end else, you end up with an up with an ethyl group.ethyl group.

ethylethyl

H HH H | | | |H-C-C- H-C-C-  | | | | H H H H

Propyl GroupsPropyl GroupsPropane has Propane has three carbons three carbons and eight and eight hydrogen hydrogen atoms. If one atoms. If one of the six end of the six end hydrogens is hydrogens is replaced by a replaced by a bond to bond to something something else, you end else, you end up with a up with a normal propyl normal propyl group. If one group. If one of the two of the two middle middle hydrogens is hydrogens is replaced by a replaced by a bond to bond to something something else, you end else, you end up with an up with an isopropyl isopropyl

group.group.

nn--propylpropyl

or or simplysimplypropyl propyl

H H HH H H | | | | | |H-C-C-C- H-C-C-C-  | | | | | | H H H H H H

isopropisopropyl yl

H H HH H H | | | | | |H-C-C-C-HH-C-C-C-H |  | | |  | | H    H H    H

Butyl GroupsButyl Groups

The next set of alkyl groups contains four carbons. The next set of alkyl groups contains four carbons. That is why they are called That is why they are called butylbutyl groups. There are groups. There are four types of butyl groups each with a different four types of butyl groups each with a different combination of carbon chain and bonding point.combination of carbon chain and bonding point.

Other Alkyl GroupsOther Alkyl Groups

The IUPAC (International Union of Pure The IUPAC (International Union of Pure and Applied Chemistry) name for and Applied Chemistry) name for Alkanes are obtained using the Alkanes are obtained using the following rules:following rules:

1. All alkanes have the 1. All alkanes have the ending –aneending –ane

2. The longest continuous 2. The longest continuous chain of carbon atoms is chain of carbon atoms is determined, and this determined, and this chain is used as the chain is used as the parent structure. parent structure.

The parent structure is The parent structure is pentane. If the chain is in pentane. If the chain is in the form of a ring, then the form of a ring, then the prefix cyclo- is used.the prefix cyclo- is used.

3. The carbon atoms in this chain are numbered by 3. The carbon atoms in this chain are numbered by starting at the end that would give the lowest starting at the end that would give the lowest numbers to the group or groups attached to the numbers to the group or groups attached to the parent structure. In the above example, the lowest parent structure. In the above example, the lowest numbers would be obtained by numbering from the numbers would be obtained by numbering from the left side (2 and 3 are lower than 3 and 4)left side (2 and 3 are lower than 3 and 4)

4. The group attached to parent structure, other 4. The group attached to parent structure, other than hydrogen, is given both name and number. than hydrogen, is given both name and number. Halogens attached to the parent structure are Halogens attached to the parent structure are named ( halo— )named ( halo— )

ClCl is is chlorochloroBrBr isis bromobromoII isis iodoiodo

NONO22 isis nitornitorAlkyl groups are given their IUPAC namesAlkyl groups are given their IUPAC names

5. If more than one of the 5. If more than one of the same group appears as a same group appears as a substitute in a given substitute in a given molecule, then the prefixes molecule, then the prefixes di, tri, tetra, and penta are di, tri, tetra, and penta are used to indicate the used to indicate the number of times this group number of times this group appears (two, three, four, appears (two, three, four, and five times)and five times)

The position of these The position of these groups on the numbered groups on the numbered parent structure is parent structure is indicated in increasing indicated in increasing numerical order. Each numerical order. Each group must have a number group must have a number to indicate its position on to indicate its position on the parent structurethe parent structure

Since 2 methyl groups are attached to the parent Since 2 methyl groups are attached to the parent structure and hence di is used (structure and hence di is used (dimethyldimethyl). The groups ). The groups are attached at the 2nd and 3rd positions, so we use are attached at the 2nd and 3rd positions, so we use ((2,3-dimethyl2,3-dimethyl). The comma ( , ) is used between ). The comma ( , ) is used between numbers and the hyphen ( - ) is used between numbers numbers and the hyphen ( - ) is used between numbers and names.and names.

6. If more than one type of group is attached to the 6. If more than one type of group is attached to the parent structure, these groups are placed in parent structure, these groups are placed in alphabetical order in the name of the compound.alphabetical order in the name of the compound.

di - , tri - , tetra - , sec - , tert – are ignored in di - , tri - , tetra - , sec - , tert – are ignored in determining the orderdetermining the order

The underlined letter is used to determine the The underlined letter is used to determine the alphabetical order in the following list of groupsalphabetical order in the following list of groupsdidicchloro , trihloro , trimmethyl , ethyl , iisopropyl , sec-sopropyl , sec-bbutyl , tert-utyl , tert-bbutyl , utyl , tetratetraeethylthyl

ExamplesExamplesName the following compounds using Name the following compounds using IUPAC namesIUPAC names

Chemical ReactionsChemical Reactions

Alkenes (Olefins)Alkenes (Olefins)

They are aliphatic hydrocarbons that They are aliphatic hydrocarbons that have the general molecular formula have the general molecular formula CnH2nCnH2n for open-chain systems for open-chain systems

The simplest alkene is the Ethylene The simplest alkene is the Ethylene ((CC22HH44))

Alkenes are unsaturated hydrocarbons, Alkenes are unsaturated hydrocarbons, since they contain fewer than the since they contain fewer than the maximum number of hydrogen atoms in maximum number of hydrogen atoms in their general formulatheir general formula

Alkenes contain a double bondAlkenes contain a double bond

Ethylene (ethene)Ethylene (ethene)

The First Alkenes Are The First Alkenes Are

NomenclatureNomenclature

ExamplesExamples

Alkynes (Acetylene Alkynes (Acetylene Series)Series)

NomenclatureNomenclature1. All have the ending –yne (IUPAC name of 1. All have the ending –yne (IUPAC name of acetylene is enthyne)acetylene is enthyne)

2. The logest continuous chain of carbon atoms that 2. The logest continuous chain of carbon atoms that contain the triple bond is used as the parent contain the triple bond is used as the parent structurestructure

3. The chain is numbered such that the triple bond 3. The chain is numbered such that the triple bond has the lowest possible numberhas the lowest possible number

4. The position of the triple bond is indicated by 4. The position of the triple bond is indicated by placing the lowest number of the carbon atom of the placing the lowest number of the carbon atom of the triple bond before the name of the parent structuretriple bond before the name of the parent structure

5. the groups attached to the parent structure, other 5. the groups attached to the parent structure, other than hydrogen, are given both name and number and than hydrogen, are given both name and number and are placed in alphabetical order.are placed in alphabetical order.

ExamplesExamples

Chemical ReactionsChemical Reactions