How to Name Substituents

Naming Substituents

A prefix must be used to identify all groups outside of the parent (chain or ring system). Such groups are called "substituents."

Saturated hydrocarbon substituents (alkyl groups) are distinguished from alkanes names by changing the -ane ending to -yl.
CH₄ is called "methane" CH₃- is called "methyl".
Some substituents still go by their trivial names.
Unsaturated hydrocarbons are modified using the same rules as alkanes.
The alkane -ane suffix is changed to -enyl or -ynyl when double bonds or triple bonds are present in the substituent.
Functional groups of lower priority than the principal functional group are named using the substituent prefix.
Multiple substituents of the same type are specified by adding the multiplicative terms (table to the right) before the prefix name.
The location along the parent chain (or ring) should always be specified if, and only if, the location is ambiguous. The "locant" is the atom number where the substituent is located.

The locant for double and triple bonds shows the position of only the first carbon atom (the second atom is assumed to be n+1).

Multiplicative Terms
(1 mono-) usually assumed
2 di-
3 tri-
4 tetra-
5 penta-
6 hexa-
7 hepta-
8 octa-
9 nona-
10 deca-
11 undeca-
12 dodeca-
20 icosa-

Note: These terms are not used in alphabetizing.

Numbering the Parent Chain

The following rules should be used, in the order given, until a numbering system is established (all subsequent rules are ignored).

The parent chain is numbered so that the principal functional group receives the lowest number
The first unsaturated carbon gets the lowest number
The first double bond gets the lowest number
The first substituent gets the lowest number
The earliest alphabetical substituent gets the lowest number

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Naming Substituents A prefix must be used to identify all groups outside of the parent (chain or ring system). Such groups are called "substituents." Saturated hydrocarbon substituents (alkyl groups) are distinguished from alkanes names by changing the -ane ending to -yl. CH₄ is called "methane" CH₃- is called "methyl". Some substituents still go by their trivial names. Unsaturated hydrocarbons are modified using the same rules as alkanes. The alkane -ane suffix is changed to -enyl or -ynyl when double bonds or triple bonds are present in the substituent. Functional groups of lower priority than the principal functional group are named using the substituent prefix. Multiple substituents of the same type are specified by adding the multiplicative terms (table to the right) before the prefix name. The location along the parent chain (or ring) should always be specified if, and only if, the location is ambiguous. The "locant" is the atom number where the substituent is located. The locant for double and triple bonds shows the position of only the first carbon atom (the second atom is assumed to be n+1).	Multiplicative Terms (1 mono-) usually assumed 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa- 9 nona- 10 deca- 11 undeca- 12 dodeca- 20 icosa- Note: These terms are not used in alphabetizing.
Numbering the Parent Chain The following rules should be used, in the order given, until a numbering system is established (all subsequent rules are ignored). The parent chain is numbered so that the principal functional group receives the lowest number The first unsaturated carbon gets the lowest number The first double bond gets the lowest number The first substituent gets the lowest number The earliest alphabetical substituent gets the lowest number
	Return to the flow chart