Experimental and theoretical study of the homogeneous, unimolecular gas‐phase elimination kinetics of methyl oxalyl chloride

Abstract

AbstractThe products of the gas‐phase elimination of methyl oxalyl chloride are methyl chloroformate and carbon monoxide. The kinetics were determined in a static system over the temperature range 280.3–320.7 °C and pressure range 56–140.4 Torr. The reaction, in vessels seasoned with allyl bromide and in the presence of the free‐radical inhibitor cyclohexene, is homogeneous, unimolecular and follows a first‐order rate law. The rate coefficients are given by the Arrhenius equation: log[k1 (s−1)]=(12.73 ± 0.58)−(174.3 ± 6.3) kJ mol−1 (2.303 RT)−1. Theoretical studies of the mechanism at the semi‐empirical PM3 and MP2/6–31G* levels imply a concerted non‐synchronous process. Analysis of the three‐membered ring transition state suggests that polarization of the ClC(O) bond is rate limiting in the elimination process. The kinetics and thermodynamic parameters are in good agreement with the experimental values. Copyright © 2004 John Wiley & Sons, Ltd.