Acetic formic anhydride

Acetic formic anhydride is an organic compound with the chemical formula, which can be viewed as the mixed anhydride of acetic acid and formic acid. It is used on a laboratory-scale as a formylating agent.

Preparation
Acetic formic anhydride can be produced by reacting sodium formate with acetyl chloride in anhydrous diethyl ether between 23–27 °C. It can also be prepared by the reaction of acetic anhydride and formic acid at 0 °C.

Properties
While more stable than formic anhydride, acetic formic anhydride is thermally unstable and gradually decomposes above about 60 °C, with the evolution of carbon monoxide. Impurities such as pyridine or residual acid can promote this, resulting in decomposition commencing as low as 0 °C. Crude material has been successfully purified by distillation at ≤30 °C under reduced pressure.

Applications
Acetic formic anhydride is a formylation agent for amines, amino acids, and alcohols. It is also a starting material for other compounds such as formyl fluoride.