Organic compounds containing -COOH as the functional group are called carboxylic acids. The -COOH group is called carboxyl group.
Classification of Carboxylic Acids
- Carboxylic acids may be aliphatic or aromatic depending upon whether the carboxyl group is attached to an alkyl group (or hydrogen)
or an aryl group.
- Carboxylic acids are further classified on the basis of the number of carboxyl group present. In this case prefixes such as mono (for one) , di (for two), poly (for many) are used.
Resonance in Carboxyl Group
The carboxyl group exhibits resonance and has three resonance structures :
Although the carboxyl group has three resonance structures, only structures (1) and (3) are considered important because in structures (1) and (3) the carbonyl carbon has complete octet whereas the carbonyl carbon of structure (2) has incomplete octet which makes it less stable.