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Kinetics and Mechanism of the Gas Phase Reaction of Atomic Chlorine with CH2ICl...

Bilde, M., J. Sehested, O. J. Nielsen, T. J. Wallington, R. J. Meagher, M. E. McIntosh, C. A. Piety, J. M. Nicovich, and P. Wine (1997), Kinetics and Mechanism of the Gas Phase Reaction of Atomic Chlorine with CH2ICl at 206-432 K, J. Phys. Chem. A, 101, 8035-8041.

The title reaction was studied using two different experimental techniques: laser flash photolysis with resonance fluorescence detection of Cl atoms and continuous photolysis with FTIR detection of end products. Over the temperature range 206-432 K the rate constant for reaction of Cl atoms with CH2ICl is given (to within (15%) by the Arrhenius expression k1 ) 4.4 × 10-11 exp(195/T) cm3 molecule-1 s-1, which gives k1 ) 8.5 × 10-11 cm3 molecule-1 s-1 at 298 K. Variation of the total pressure of N2 diluent over the range 5-700 Torr at 295 K had no discernible (<10%) effect on the rate of reaction. At 295 K in 100-700 Torr of N2 the reaction proceeds via iodine transfer to give CH2Cl radicals. As part of this work the rate constant k(CH2Cl+O2+M) was measured at 295 K in the presence of 1-800 Torr of N2 diluent. The results were well described by the Troe expression with a broadening factor Fc of 0.6 and limiting low- and high-pressure rate constants of k0 ) (1.8 ( 0.1) × 10-30 cm6 molecule-2 s-1 and k∞ ) (3.3 ( 0.3) × 10-12 cm3 molecule -1 s-1. The results are discussed with respect to the available literature for reactions of Cl atoms with halogenated organic compounds and the potential role of the title reaction in atmospheric chemistry.

Research Program: 
Upper Atmosphere Research Program (UARP)