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 ka 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 ka 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 ka over a much wider range of pressure than has been used to date. More work is also required to validate the strong collision assumption.