What is "acetic anhydride"

n. (context organic compound English) The acid anhydride of acetic acid, (CH₃CO)₂O.

n. a compound that is needed in order to refine opium into heroin

Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CHCO)O. Commonly abbreviated AcO, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a colorless liquid that smells strongly of acetic acid, which is formed by its reaction with moisture in the air.