Chloroformic acid is a chemical compound with the formula ClCO2H.

It is described as unstable, decomposing into carbon dioxide and hydrogen chloride.

[3] Chloroformic acid itself is too unstable to be handled for chemical reactions.

However, many esters of this carboxylic acid are stable and these chloroformates are important reagents in organic chemistry.

[4] They are used to prepare mixed carboxylic acid anhydrides used in peptide synthesis.