A two-center model of the concerted molecular decomposition of unsaturated compounds

Abstract

A semiempirical model of the concerted decomposition of unsaturated compounds (olefins, alcohols, acids, and ethers) and aliphatic esters into two molecules is suggested. The model considers the decomposition reaction as a single-step transfer of the hydrogen atom in one reaction center and the dissociation of a C-C or C-O bond in the other accompanied by a shift of π electrons in the cyclic six-membered transition state. Each elementary event in such a concerted reaction is characterized by its own activation energy, Eabs for the transfer of H, E>d for bond dissociation, and Eπ for the shift of π bonds. The Eabs and Ed activation energies were calculated by the method of intersecting parabolas. The spectrum of activation energies (sets of the Eabs, Ed, and Eπ values) for each of 45 decomposition reactions was calculated with the use of experimental data. The contribution of enthalpy to the activation energy of each event was estimated.