Kinetics and mechanism of the gas phase reaction of atomic chlorine with CH2ICl at 206-432 K

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 x 10(-11) exp(195/T) cm(3) molecule(-1) s(-1), which gives k(1) = 8.5 x 10(-11) cm(3) molecule(-1) s(-1) at 298 K. Variation of the total pressure of N-2 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 N-2 the reaction proceeds via iodine transfer to give CH2Cl radicals. As part of this work the rate constant k(CH2Cl+O-2+M) was measured at 295 K in the presence of 1-800 Torr of N-2 diluent. The results were well described by the Tree 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) x 10(-30) cm(6) molecule(-2) s(-1) and k(infinity) = (3.3 +/- 0.3) x 10(-12) cm(3) molecule(-1) s(-1). The results are discussed with respect to the available literature for reactions of CI atoms with halogenated organic compounds and the potential role of the title reaction in atmospheric chemistry.