Quantum chemical and kinetic study of the reaction between CCl2 and NO2 radicals

Abstract

The dependence of the rate constant of the recombination reaction of CCl2 and NO2 radicals on temperature and pressure was studied. Quantum-chemical calculations were employed to characterize relevant aspects of the potential energy surface for this process. The limiting rate constants between 300 and 2000 K were analyzed using the unimolecular reactions theory. The resulting low pressure rate constant can be represented as k0 = [He] (1.4 ± 0.2) x 10-26 (T/300 K)(-8.72±0.04)exp(-(1520 ± 10) K/T) cm3 molecule-1 s-1. The corresponding expressions for the high pressure limit rate constants, derived from a simplified version of the statistical adiabatic channel (SSACM) and from a SACM combined with classical trajectory calculations (SACM/CT), are (2.3 ± 1.9) x 10-11 (T/300 K)(-1.01±0.39)exp(-(810 ± 80) K/T) and (8.8 ± 5.3) x 10-13 (T/300 K)(0.82±0.13) cm3 molecule-1 s-1. The falloff curves were represented in terms of these limiting rate constants. Reported experimental results are well described with the present model. Our calculations indicate that the CCl2 + NO2 reaction proceeds via the stabilization of the energized CCl2NO2 adduct, and that the CCl2 + NO2 → CCl2O + NO channel becomes relevant at high temperatures.