The gas-phase reaction of methyl acetate and hydrogen bromide

Abstract

In the gas phase methyl acetate reacts with hydrogen bromide over the range 419-497° to give methyl bromide, carbon monoxide, and methanol. Rate constants first order in both ester and hydrogen bromide are calculated from initial slopes, and are described by the equation                      k₂ = 10^12.29exp(-32312/RT) ml mol^-1 s^-1 Kinetic data depart from this second-order form at early stages of the reaction. The addition of methanol can reduce the value of k₂ to zero. A mechanism involving the reversible step :                          CH₃COOCH₃+HBr ↔ CH₃OH+A* is proposed. The intermediate reacts with isobutene to form mesityl oxide, and is considered identical with that formed in the reaction of acetic acid with hydrogen bromide.