They are classified based on the number of carboxyl groups per molecule.
1. Monocarboxylic acids – They have one carboxyl group per molecule.
e.g. CH3COOH i.e. ethanoic acid
2. Dicarboxylic acids – They have two carboxyl groups per molecule.
e.g. ethanoic acid
C – OOH
C – OOH
3. Tricarboxylic acids – They have three carboxyl groups per molecule. E.g. 2 – hydroxy propane – 1,2,3, – tricarboxylic acid.