Issue 9, 1976

The thermal decomposition of propanoic and 2-methylpropanoic anhydrides in the gas phase

Abstract

The homogeneous gas-phase thermal decompositions of propanoic anhydride and 2-methylpropanoic anhydride have been studied over the temperature ranges 220–294 and 246–283 °C respectively. Both reactions obey first-order kinetics, are unaffected by chain inhibitors and give the parent acid and methylketen or dimethylketen respectively as sole products.

Kinetic parameters are given by the equations k/s–1= 1011.38 exp (–140 400 J mol–1/RT) in the case of propanoic anhydride, and k/s–1= 1011.81 exp (–151 500 J mol–1/RT) for 2-methylpropanoic anhydride. Equilibrium constants were also measured in the propanoic anhydride system and gave ΔH°= 95 095 J mol–1 and ΔS°= 132.2 J K–1 mol–1 in the direction of decomposition. The effect of alkyl substitution on the transition states for anhydride decomposition is discussed.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 2, 1976, 986-987

The thermal decomposition of propanoic and 2-methylpropanoic anhydrides in the gas phase

P. G. Blake, A. Craggs and M. B. Vayjooee, J. Chem. Soc., Perkin Trans. 2, 1976, 986 DOI: 10.1039/P29760000986

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