Propionic anhydride

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 as well as for producing specialty derivatives of cellulose.[1]

Propanoic anhydride

Names
Preferred IUPAC name Propanoic anhydride
Other names Propionic anhydride Propanoyl propanoate
Identifiers
CAS Number	123-62-6
3D model (JSmol)	Interactive image
ChemSpider	29003
ECHA InfoCard	100.004.218
PubChem CID	31263
RTECS number	UF9100000
UNII	E3A2VV18E6
CompTox Dashboard (EPA)	DTXSID1027007
InChI InChI=1S/C6H10O3/c1-3-5(7)9-6(8)4-2/h3-4H2,1-2H3 Key: WYVAMUWZEOHJOQ-UHFFFAOYSA-N InChI=1/C6H10O3/c1-3-5(7)9-6(8)4-2/h3-4H2,1-2H3 Key: WYVAMUWZEOHJOQ-UHFFFAOYAJ
SMILES CCC(=O)OC(=O)CC
Properties
Chemical formula	C6H10O3
Molar mass	130.14 g/mol
Appearance	Clear liquid, with a strong smell similar to vinegar
Density	1.015 g/cm^3, liquid
Melting point	−42 °C (−44 °F; 231 K)
Boiling point	167 to 170 °C (333 to 338 °F; 440 to 443 K)
Solubility in water	Reacts to give propanoic acid
Viscosity	1.144 cP at ?°C
Hazards
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R-phrases (outdated)	R34
S-phrases (outdated)	S26-45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 Propanoyl chloride
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

Synthesis

Industrial route to propionic anhydride involves thermal dehydration, driving off the water by distillation:

2 CH₃CH₂CO₂H → (CH₃CH₂CO)₂O + H₂O

Another routes is the Reppe carbonylation of ethylene with propionic acid and nickel carbonyl as the catalyst:[1]

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

Propionic anhydride has also been prepared by dehydration of propionic acid using ketene:[2]

2 CH₃CH₂CO₂H + CH₂=C=O → (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 Administration as a List I chemical under the Controlled Substances Act.[3]

References

1. Samel, Ulf-Rainer; Kohler, Walter; Gamer, Armin Otto; Keuser, Ullrich (2005). "Propionic Acid and Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_223.
2. Williams, J. W. Krynitsky, J. A. (1955). "n-Caproic Anhydride". Organic Syntheses.CS1 maint: multiple names: authors list (link); Collective Volume, 3
3. Drugs of Abuse Publication, Chapter 2 Archived 2007-12-20 at the Wayback Machine