12.4: Common Names of Aldehydes and Ketones

Some common aldehydes and ketones are popularly known by their common names used historically and predate the IUPAC nomenclature.

Common names of aldehydes are derived from the names of their corresponding acid. For instance, the two-carbon aldehyde–acetaldehyde derives its name from the corresponding acid–acetic acid. Similarly, formaldehyde derives its name from formic acid and benzaldehyde from benzoic acid.

Aliphatic ketones are named by suffixing the word “ketone” to the alphabetically arranged names of the groups that flank the carbonyl group. For instance, the ketone below has methyl and ethyl groups on either side of the carbonyl group. Hence the compound is named ethyl methyl ketone.

Some aromatic ketones are named “phenones”. The word phenone is prefixed with the name of the acyl group attached to the aromatic ring. Depending upon the alkyl or aryl group present, different names are given to the acyl groups. For instance, if the methyl group is present, the compound gets the name acetophenone, and the presence of the phenyl group gives the name benzophenone.

Common names of aldehydes are derived by suffixing 'aldehyde' to the common parent names of corresponding carboxylic acids.

For instance, acetaldehyde derives its name from acetic acid, and benzaldehyde acquires its name from benzoic acid.

Common names of aliphatic ketones include the names of the two flanking groups arranged in alphabetical order, followed by the suffix 'ketone'.

Some aromatic ketones are named 'phenones' such that the word phenone is prefixed by the name of the acyl group.  

Depending on the identity of the 'R' in the acyl group, different ketones acquire different common names.

For example, an aromatic ketone with methyl as the 'R' group is called acetophenone, whereas a benzene ring as the 'R' group gives the name benzophenone.

In aldehydes and ketones, the locants in the common names are represented by Greek letters starting from the carbon atom adjacent to the carbonyl carbon.

The hydrogen atoms linked to these carbons are also indicated with the same greek letters.