Propanoic anhydride

Propanoic anhydride, also called propionic anhydride, is a simple acid anhydride. With the chemical formula (CH3CH2CO)2O, it is a widely used reagent in organic synthesis.

Synthesis
Propionic anhydride has been prepared by dehydration of propionic acid using ketene:
 * 2 CH3CH2CO2H +  CH2=C=O  &rarr;  (CH3CH2CO)2O  +  CH3CO2H

Safety
Propanoic anhydride is strong smelling and corrosive, and will cause burns on contact with skin. Vapour can burn eyes and lungs.

Legal Status
Due to its potential use as a precursor in the synthesis of fentanyl and fentanyl analogs, propanoic anhydride is regulated by the United States Drug Enforcement Agency as a List I chemical under the Controlled Substances Act.