Naming specific functional groups |

Download a printable version of this document here

Tip;

Alkanes, Alkenes, Alkynes

Tip; the suffix for alkenes can go in front of other suffixes.

Haloalkanes

Class a halogen as a substituent on the C chain and therefore use related suffix.

Have the suffix -ol and if necessary the position number for the OH group is added between the name stem and the –ol.
If the compound has an –OH group in addition to other functional groups that need a suffix ending then the OH can be named with the prefix hydroxy-.

Remember if there are two or more -OH groups then di, tri etc are used, therefore ADD the ‘e’ on to the stem name!

Amines

Have the suffix -amine. However, rather confusingly there are two ways in which an amine can be written using this suffix. In the “common version” the name stem ends in -yl e.g. propylamine. The IUPAC version of the same chemical is propan-1-amine (i.e. using the same labelling method as naming alcohols).

If the amine is secondary (i.e. has two alkyl groups attached to the nitrogen), each chain is named and the smaller alkyl group is preceded by a N- which plays the same role as a number in the positioning of a branched alkyl chain.
- In the common naming version if the chain lengths are the same an –N is not used.
- If a tertiary amine similar rules apply and each alkyl side group is given an N.
If other high priority functional groups are present the amino- prefix is used.

Nitriles

Have the suffix –nitrile, but the C of the CN group counts as the first carbon of the chain.

Have the prefix cyano- when naming molecules with higher priority groups.
A common version of naming also uses the -cyanide suffix, but this can be confusing as it uses a different method to count the carbons on a molecule!

Aldehydes & ketones

An aldehyde’s suffix is -al. It always has the C=O bond on the first carbon of the chain so it does not need an extra number (i.e. its by default number one on the chain).
Have the prefix formyl- when naming molecules with higher priority groups.

A Ketones suffix is-one. When ketones are part of a 5 carbon or more chain, you then it need a number to show the position of the carbonyl.
If there are 2 ketone groups then di is put before –one and remember to add an e to the stem.
The prefix oxo- should be used for compounds that contain a ketone group in addition to a carboxylic acid or aldehyde group.

Carboxylic acids & their derivatives

Carboxylic acids have the suffix -oic acid but no number is necessary for the acid group as it must always be at the end of the chain (the numbering always starts from the carboxylic acid end).
If there are carboxylic acid groups on both ends of the chain then it is called a – dioic acid therefore do not forget the “e”!

Esters have two parts to the name, the part ending in –yl comes from the alcohol that has formed it and is next to the oxygen. The part ending in –anoate comes from the carboxylic acid (this is the chain, including the C=O bond).
Acid anhydrides have the suffix -oic anhydride. If the alkyl groups are of different lengths then each one is named.

Acyl chlorides have the suffix -oyl chloride. Like the other groups when there is di substituents, remember the “e”!
Amides have the suffix -amide. Secondary and tertiary amides are labelled with the same method as amines, where the name is preceded by an N- (which plays the same role as a number in positioning a side alkyl chain).

Tip; for aldehydes, carboxylic acids & nitriles, the functional group is always on carbon 1!

To go back to the rules of naming function groups, go to the chemBAM page.

To test your knowledge on naming molecules see this chemBAM quiz.

Tip; for aldehydes, carboxylic acids & nitriles, the functional group is always on carbon 1!