Propionic anhydride

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Propanoic anhydride
Propanoic anhydride.png
CAS number 123-62-6 YesY
PubChem 31263
ChemSpider 29003
RTECS number UF9100000
Jmol-3D images Image 1
Molecular formula C6H10O3
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
Boiling point 167–170 °C
Solubility in water Reacts to give propanoic acid
Viscosity 1.144 cP at ?°C
MSDS External MSDS
R-phrases R34
S-phrases S26-45
Main hazards flammable
Flash point 63 °C (145 °F; 336 K)
Related compounds
Related compounds Acetic anhydride
Except where noted otherwise, 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", Org. Synth. ; Coll. Vol. 3 
  2. ^ Drugs of Abuse Publication, Chapter 2