Anchimeric assistance of the CO2CH3 substituent in the elimination kinetics of 3-(methoxycarbonyl)propyl methanesulfonate in the gas phase

Abstract

The elimination kinetics of 3-(methoxycarbonyl)propyl methanesulfonate have been determined in a static system over the temperature range of 289.3–329.8 °C and pressure range of 43–111 torr. The reaction, in vessels seasoned with allyl bromide and in the presence of at least an equal amount of the free radical suppressor toluene, is homogeneous, unimolecular and first-order kinetically. The rate coefficients follow the Arrhenius equation: log k₁=(13.50 ± 0.47)–(182.2 ± 5.3)(2.303 RT)^–1. A very high extent of lactone formation suggests an unequivocal participation of the carbonyl oxygen of the CO₂CH₃ group. The partial rates for the parallel elimination towards the formation of butyrolactone and a small amount of methylbut-3-enoate have been estimated, reported, and discussed. The present results provide further evidence of intimate ion pair mechanisms in the gas phase pyrolyses of special types of organic molecules.