Carboxylic acids: structures and reactions

Recognising the acid group

Carboxylic acids contain the –COOH group: a carbon atom double bonded to one oxygen and single bonded to an OH group. The first four are methanoic, ethanoic, propanoic and butanoic acid. Their condensed formulae are HCOOH, CH₃COOH, CH₃CH₂COOH and CH₃CH₂CH₂COOH. The carbon in COOH is part of the total carbon count, so ethanoic acid has two carbons, not three.