Kinetics and Mechanism of the Gas Phase Reaction of Atomic Chlorine with CH2ICl at 206−432 K

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 101; no. 43; pp. 8035 - 8041
• Main Authors: Bilde, M, Sehested, J, Nielsen, O. J, Wallington, T. J, Meagher, R. J, McIntosh, M. E, Piety, C. A, Nicovich, J. M, Wine, P. H
• Format: Journal Article
• Language: English
• Published: American Chemical Society 23.10.1997
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp9717960

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 k 1 = 4.4 × 10-11 exp(195/T) cm3 molecule-1 s-1, which gives k 1 = 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 F c of 0.6 and limiting low- and high-pressure rate constants of k 0 = (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.