Kinetics of the Gas-Phase Elimination Reaction of Benzyl Chloroformate and Neopentyl Chloroformate

Abstract

The gas-phase eliminations of benzyl chloroformate (475–523 K, 31–103 Torr) and neopentyl chloroformate (563–622 K, 37–70 Torr), in a deactivated static reaction vessel, and in the presence of a free radical suppressor, are homogeneous, unimolecular, and follow a first-order rate law. The rate coefficients are expressed by the following Arrhenius equations: Benzyl chloroformate Neopentyl chloroformate Formation of neopentyl chloride: Formation of 2-methylbutenes: The derived kinetic and thermodynamic parameters for benzyl chloroformate decomposition indicate the reaction proceeds through a concerted four-membered cyclic transition state to give benzyl chloride and CO2 gas. Neopentyl chloroformate undergoes a parallel reaction, where neopentyl chloride formation may arise from a polar-concerted four-membered cyclic transition state, whereas the mixture of olefins, 2-methyl-2-butene, and 2-methyl-1-butene appears to be produced from a carbene intermediate. This intermediate seems to be originated from a concerted five-membered cyclic transition state of the neopentyl substrate.