Branched-Chain Acyclic Hydrocarbons

1. Select and name the parent hydrocarbon
(a) For saturated hydrocarbons,

Parent chain: longest possible straight chain
branched chain: all remaining e.g,

(b) For unsaturated hydrocarbons,

Parent chain: longest possible straight chain which contains the maximum number of multiple bonds

(c) The parent hydrocarbon is named as described in the naming of straight-chain acyclic hydrocarbons

2. Name the branched chains

(a) The number of carbon atoms in a branched chain is indicated by the stem names

(b) The suffix ‘-yl’ is added to the corresponding stem names for branched chains containing only single bonds.

e.g. – CH₃ Methyl

– CH₂CH₃ Ethyl – CH₂CH₂CH₃ Propyl

Isopropyl or sec- Propyl (secondary)

Butyl

sec -Butyl (for secondary carbon, 2⁰)

Isobutyl

tert -Butyl (for tertiary carbon, 3⁰)

3. Numbering carbon atoms in the parent hydrocarbon
(a) For saturated hydrocarbons, the parent hydrocarbon is numbered beginning with the end of the chain nearer the branched chain. e.g.

(b) For unsaturated hydrocarbons, the parent hydrocarbon is numbered so as to include both carbon atoms of the double or triple bond. The numbering begins with the end of the chain nearer the double or triple bond.

e.g.

4. Use the numbers to designate the position of the branched chain.

The parent name is placed last, and the branched chain, preceded by the number designating its position on the parent chain, is placed first.
e.g.

5. When two or more branched chains are present, a number corresponding to its position on the parent hydrocarbon is given to each branched chain so as to give the lowest possible numbers to the branched chains. The branched chains are listed alphabetically (i.e. ethyl before methyl). Multiplying prefixes such as ‘di’ and ‘tri’ are ignored when deciding the alphabetical order.
e.g.

6. When two branched chains are present on the same carbon atom, use that number twice. e.g.

7. When two or more branched chains are identical, indicate this by the use of the prefixes ‘di-’, ‘tri-’, ‘tetra-’, and so on. Commas are used to separate numbers from each other. e.g.

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