Carboxylic acids and esters

Abstract

Carboxylic acids are structurally like aldehydes (H-C=O) and ketones (C-C=O) in that they contain the carbonyl group (C=O). However, an important structural difference is that carboxylic acids contain a hydroxyl group (-OH) attached to the carbonyl carbon. In turn this functional group is called the carboxyl group (HO-C=O). This combination gives the group an important characteristic; it behaves as an acid.