Decomposition of activated chloroalkyl radicals. Calculations by the Marcus-Rice theory

Abstract

We have calculated the A-factors A₂ for the addition of Cl to ethylene and its chlorinated derivatives using transition state theory, and the rate constant k_a for the decomposition of the activated chloroalkyl radicals ACl^* formed in reaction (2) at 308–406°K and pressures from zero to infinity by the Marcus-Rice theory. The calculated values are compared with experimental values. The agreement is within an order of magnitude. The calculated values of k_a are low for the least substituted ethylenes, agree well with experimental values for trichloroethylene, and are high for tetra-chloroethylene. The calculated values of A₂ are low except for C₂H₄ and C₂Cl₄. We conclude that more theoretical work is required to enable models used in calculation to be chosen less arbitrarily, and more experimental work to provide precise values of k_a over a much wider range of pressure than has been used to date. More work is also required to validate the strong collision assumption.