Propionic anhydride

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Propanoic anhydride
Propanoic anhydride.png
Preferred IUPAC name
Propanoic anhydride
Other names
Propionic anhydride
Propanoyl propanoate
3D model (JSmol)
ECHA InfoCard 100.004.218
RTECS number UF9100000
Molar mass 130.14 g/mol
Appearance Clear liquid, with a strong smell similar to vinegar
Density 1.015 g/cm3, liquid
Melting point −42 °C (−44 °F; 231 K)
Boiling point 167 to 170 °C (333 to 338 °F; 440 to 443 K)
Reacts to give propanoic acid
Viscosity 1.144 cP at ?°C
Main hazards flammable
Safety data sheet External MSDS
R-phrases (outdated) R34
S-phrases (outdated) S26-45
Flash point 63 °C (145 °F; 336 K)
Related compounds
Related compounds
Acetic anhydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Propanoic anhydride is an organic compound with the formula (CH3CH2CO)2O. This simple acid anhydride is a colourless liquid. It is a widely used reagent in organic synthesis.


Propanoic anhydride has been prepared by dehydration of propanoic acid using ketene:[1]

2 CH3CH2CO2H + CH2=C=O → (CH3CH2CO)2O + CH3CO2H


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

Legal Status[edit]

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 Administration as a List I chemical under the Controlled Substances Act.[2]


  1. ^ Williams, J. W. Krynitsky, J. A. (1955). "n-Caproic Anhydride". Organic Syntheses.; Collective Volume, 3
  2. ^ Drugs of Abuse Publication, Chapter 2 Archived 2007-12-20 at the Wayback Machine.