`CH_(3)COOH+underset("Ketene")( H_(2)C=C=O)to(CH_(3)CO)_(2)O`
[Ketene is prepared by pyrolysis of acetone,
`CH_(3)COCH_(3)overset(973K)toCH_(4)+CH_(2)=C=O`]
When the mixture of acetic anhydride and the carboxylic actd is distilled, anhydrides are formed.
`2RCOOH+(CH_(3)CO)_(2)Oto(RCO)_(2)O+2CH_(3)COOH`