Propionic anhydride

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Propionic anhydride
Propionic anhydride skeletal structure.png
IUPAC name
Propanoic anhydride
Other names
Propanoic acid, anhydride
Propanoyl propanoate
Jmol-3D images Image
Molar mass 130.14 g/mol
Appearance Colorless liquid
Odor Pungent, rancid odor
Density 1.015 g/cm3 (20 °C)
Melting point −42 °C (−44 °F; 231 K)
Boiling point 167–170 °C (333–338 °F; 440–443 K)
Slowly hydrolyzes
Solubility Miscible with chloroform, diethyl ether, ethanol, isopropanol, methanol
Slightly soluble in CCl4
Vapor pressure 1.36 mm Hg at 25 °C
Safety data sheet Sigma-Aldrich
Flash point 63 °C (145 °F; 336 K)
Lethal dose or concentration (LD, LC):
2,360 mg/kg (rat, oral)
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).
Infobox references

Propanoic anhydride or propionic anhydride is an organic compound with the formula (CH3CH2CO)2O.



Propanoic anhydride slowly hydrolyzes in water to propionic acid.


Propionic anhydride is a colorless liquid, with a strong pungent smell, which is insoluble in water, but slowly hydrolyzes upon contact. It is miscible with most organic solvents.


Propionic anhydride is sold by chemical suppliers.

In the US, is it classified as a List I compound, due to its use in the illicit manufacturing of fentanyl and its analogues. As such it cannot be acquired by private individuals, and a license is required to purchase and use the compound.


Propionic anhydride can be easily prepared by dry distilling a mixture of dry calcium propionate and propionyl chloride.

Alternatively, distilling a mixture propionic acid and oxalyl chloride will produce propionic anhydride, with a yield of 51%.[1]

Propanoic anhydride can also be obtained by dehydration of dry propionic acid using ethenone.

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

Another route is the Reppe carbonylation of ethylene with propionic acid and nickel carbonyl as the catalyst:[2]

CH2=CH2 + CH3CH2CO2H + CO → (CH3CH2CO)2O


  • Make esters



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


In closed bottles, away from moisture.


Can be neutralized by adding it in a diluted NaOH or KOH solution, which causes it to hydrolyze to propionic acid and finally sodium or potassium propionate, respectively, which is harmless and can be poured down the drain or dumped in soil.



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