Structure• Hydrocarbon: a compound composed only of carbon and

hydrogen

• Saturated hydrocarbon: a hydrocarbon containing only single bonds

• Alkane: a saturated hydrocarbon whose carbons are arranged in a chain

• Aliphatic hydrocarbon: another name for an alkane

Structure• Shape

– tetrahedral about carbon– all bond angles are approximately

109.5°

Nomenclature• Alkanes have the general formula CnH2n+2

Condensed Structural Formula

Molecular FormulaName

heptane

hexane

pentane

butane

propaneethanemethane CH4 CH4

C2H6 CH3CH3C3H8 CH3CH2CH3C4H10 CH3(CH2)2CH3C5H12 CH3(CH2)3CH3C6H14 CH3(CH2)4CH3C7H16 CH3(CH2)5CH3

Nomenclature• Alkanes (contd.)

tetradecane

hexadecane

octadecaneeicosane

decane

nonane

octane C8H18 CH3(CH2)6CH3C9H20 CH3(CH2)7CH3C10H22 CH3(CH2)8CH3

C14H30 CH3(CH2)12CH3C16H34 CH3(CH2)14CH3C18H38 CH3(CH2)16CH3C20H42 CH3(CH2)18CH3

dodecane C12H26 CH3(CH2)10CH3

Constitutional Isomerism• Compounds isomers: compounds with the

same molecular formula but a different connectivity (order of attachment of their atoms)– example: C4H10

CH3CH2CH2CH3 CH3CHCH3

CH3

Butane 2-Methylpropane

Constitutional Isomerism

4,111,846,763

4,347

75

3

1

Constitutional Isomers

Molecular Formula

CH4

C5H12

C10H22

C15H32

C30H62

World populationis about6,000,000,000

Nomenclature

• International Union of Pure and Applied Chemistry (IUPAC)

• Prefix tells the number of carbon atoms

• Suffix -ane specifies an alkane

Nomenclature• IUPAC system

undec-dodec-

tetradec-pentadec-hexadec-heptadec-

nonadec-eicos-

tridec-

11121314151617

octadec- 181920

Prefixmeth-eth-prop-but-pent-hex-

oct-non-dec-

1234567hept-89

10

Carbons

CarbonsPrefix

Nomenclature

• Parent name of the longest carbon chain is “alkane”

• Groups attached to the parent chain are called substituents

• Each substituent is given a name and a number– If substituent occurs more than once, di-, tri-, tetra-,

etc.

Nomenclature

• Number the chain to give the substituent encountered first the lowest number

• If there are different substituents, list them in alphabetical order. The following are not included in alphabetization.– di-, tri-, tetra-, etc.– hyphenated prefixes, such as sec- and tert-

Nomenclature

• Alkyl groups

isopropyl

propyl

ethyl

methyl

Condensed Structural Formula

Name

CH3

-CH2CH3

-CH3

-CH2CH2CH3

-CHCH3

Nomenclature• Alkyl groups

tert-butyl

sec-butyl

isobutyl

butyl

CH3

CH3CH3

CH3

-CH2CH2CH2CH3

-CH2CHCH3

-CHCH2CH3

-CCH3

Condensed Structural Formula

Name

Nomenclature

• Alkyl groups

neopentyl

isopentyl

pentyl

CH3

CH3

CH3

-CH2CH2CH2CH2CH3

-CH2CH2CHCH3

-CH2CCH3

Condensed Structural Formula

Name

Nomenclature1. The general name of an open-chain satuated

hydrocarbon is alkane

2. For branched-chain hydrocarbons, the alkane corresponding to the longest chain is taken as the parent chain and its name is the root name

3. Groups attached to the parent chain are called substituents. Each is given a name and a number

CH3CHCH3

CH3

2-Methylpropane

1 2 3

Nomenclature

4. If there is more than one substituent, number from the end of th chain that gives the substituent encountered first the lower number

2-Methylpentane

CH314 3 25

CH3CH2CH2CHCH3

Nomenclature5. If the same substituent occurs more than once, the

number of each carbon of the parent chain on which it occurs is given and the number of times it occurs is shown by di-, tri-, tetra-, etc.

6. If there are two identical substituents, number the chain to give the lower number to the substituent encountered first

CH3CHCH2CHCH3

CH3

2,4-Dimethylpentane

CH31 2 3 4 5

Nomenclature

7. If there are two or more different substituents, list them in alphabetical order, and number from the end of the chain that gives the substituent encountered first the lower number

CH3CH2CHCH2CHCH2CH3

3-Ethyl-5-methylheptane

CH3654321

CH2CH3

7

Nomenclature8. The prefixes di-, tri-, tetra- etc. are not included in

alphabetization

9. Neither are italicized prefixes such as sec- and tert-.

CH3CCH2CHCH2CH3

CH3

4-Ethyl-2,2-dimethylhexane

1 2CH2CH3

CH3

3 4 5 6

Classification of C & H• Primary (1°) C: a carbon bonded to one other carbon

– 1° H: a hydrogen bonded to a 1° carbon

• Secondary (2°): a carbon bonded to two other carbons– 2°H: a hydrogen bonded to a 2° carbon

• Tertiary (3°) C: a carbon bonded to three other carbons– 3° H: a hydrogen bonded to a 3° carbon

• Quaternary (4°) C: a carbon bonded to four other carbons

Cycloalkanes• General formula CnH2n

• Structure and nomenclature– to name, prefix the name of the corresponding open-

chain alkane with cyclo-, and name each substituent on the ring

– if only one substituent, no need to give it a number– if two or more substituents, number from the substituent

of lowest alphabetical order– where there is choice, number to give substituents the

lowest set of numbers

Cycloalkanes

• Line-angle drawings– each line represents a C-C bond– each angle represents a C

C

C CC

CCC

CH2C

H2C C

CH

C

CH

H2

H2 CH3

CH3

Cycloalkanes• Examples: name these cycloalkanes

a) b)

c) d)