Kinetics of the CHCl2 and CH2Cl Association Reactions with Molecular Oxygen between 298 and 448 K and from 1 to 760 Torr of Total Pressure

Article abstract of DOI:10.1021/j100120a023

The rate constants for the recombination reactions between molecular oxygen and the halogenated methyl radicals CHCl2 and CH2Cl were determined over the pressure range of 1 to 760 Torr in nitrogen as a function of temperature.The CHCl2 + O2 reaction (1) was studied over the temperature range 298 < T/K < 383 and the CH2Cl reaction (2) over the range 298 < T/K < 448.The large range in pressure was attained by using two complementary techniques: Low-pressure experiments (1-10 Torr) were concluded using laser photolysis / photoionization mass spectrometry.High-pressure experiments (20-760 Torr) were carried out with the laser photolysis / UV absorption spectroscopy technique.A nonvariational RRKM calculation using previously determined thermodynamic parameters for these two reactions was performed, providing a complete and coherent picture of the kinetics and equilibria for these reactions.In addition, the data were fitted to a simplified and commonly used form of an expression developed by Troe to extrapolate falloff data to obtain high- and low-pressure limiting rate constants.Parameters are provided that allow the calculation of the rate constants of the title reactions as a function of temperature and pressure.The data are well represented by the following limiting rate-constant expressions: reaction 1, k₀(T) = (1.26+/-0.03)*10^-30(T/300)^-4.0+/-0.2 cm⁶*molecule^-2*s^-1, k₀₀(T) = (2.8+/-0.2)*10^-12(T/300)^-1.4+/-0.3 cm³*molecule^-1*s^-1; reaction 2, k⁰(T) = (1.88+/-0.05)*10^-30(T/300)^-3.2+/-0.2 cm⁶*molecule^-2*s^-1, k₀₀(T) = (2.9+/-0.2)*10^-12(T/300)^-1.2+/-0.4 cm³*molecule^-1*s^-1.