Kinetic and Modeling Studies of the Reaction of Hydroxyl Radicals with the Chloroethylenes at Low to Intermediate Temperatures

摘要

Absolute rate coefficients for the reaction of hydroxyl radicals with chloroethylene, 1,1- and trans-1,2-dichloroethylene, trichloroethylene and tetrachloroethylene are reported. Rate measurements were obtained using a laser photolysis/laser-induced fluorescence (LP/LIF) technique under slow flow conditions. Temperature ranges typically varied from 291 to 750 K. All measurements were recorded at atmospheric pressure. Ambient rate coefficients were in accord with prior measurements. The temperature dependence of the rate coefficients varied with chlorine substitution. The results were interpreted in terms of the relative importance of OH addition versus H atom abstraction pathways. For chloroethylene and 1,1-dichloroethylene, OH addition (with adduct stabilization) dominates at low temperatures and H-atom abstraction dominates above 700 K. For trans-1,2-dichloroethylene, trichloroethylene and tetrachloroethylene, chemically activated OH addition followed by Cl atom elimination is the dominant pathway at all but the lowest of temperatures. Kinetic isotope effect measurements support the absence of H-atom abstraction at elevated temperatures for trichloroethylene. The kinetic data were modeled with ab initio theory and Quantum RRK analysis. Arrhenius parameters for the individual compounds and the major reaction pathways based on QRRK modeling will be presented and discussed. The relevance of these new measurements to atmospheric and incineration chemistry will also be discussed.