Kinetics of the thermal gas-phase decomposition of methoxycyclopropane

Abstract

In the temperature range 635–694 K, 70–80% of the methoxycyclopropane decomposing initially results in the formation of the isomerization products (E)-and (Z)-1-methoxyprop-1-ene and 3-methoxyprop-1-ene. The residual decomposition results from approximately equal contributions from methyl–oxygen bond fission and the subsequent radical abstraction reactions. The isomerization products are formed by homogeneous, non-radical, unimolecular pathways with high-pressure rate constants given by the equations k[(E)-+(Z)-1-methoxyprop-1-ene]/S^–1= 10^{13.29 ± 0.75} exp (–226.5 ± 9.5 kJ mol^–1/RT) and k(3-methoxyprop-1-ene)/S^–1= 10^{14.0 ± 1.1} exp (–254 ± 14 kJ mol^–1/RT).

The methoxy group lowers the activation energy for opening the cyclopropane ring adjacent to the point of substitution by ca. 45 kJ mol^–1.