Reactions of Keten. Part VI. Kinetics of gas-phase reactions with halogenated and unsaturated acids, formic acid, and acetic [2H]acid

Abstract

The homogeneous bimolecular reactions of keten with carboxylic acids in the gas phase have been studied for halogenated and unsaturated acids, and formic acid. Rates increase proportionately to the increase in intrinsic strength of the acid, except for the very strongest acids which react more rapidly than expected. A large deuterium isotope effect is found at the acid hydrogen atom. Reactions with dimethylketen are slower than with keten by a factor of 2.4. A concerted but non-synchronous mechanism involving a six-centre transition state is proposed. The results and mechanism are compared with those for ester decomposition and for the reactions of dimethylketen with acids in solution.