Theoretical Investigation of the Reaction of O(3P) with CH2Cl

The reaction of oxygen atom with chlorinated methyl radical has been studied using the G2MP2 level of theory. The computation reveals an association−elimination mechanism. The addition reaction of O( 3 P) with CH 2 Cl proceeds to the formation of an energy-rich intermediate OCH 2 Cl*. Four product channels of OCH 2 Cl* are found: H + CHClO, Cl + CH 2 O, CHClOH, and H 2 + ClCO. The isomer CHClOH also has four product channels: H + CHClO, HCl + HCO, H 2 + ClCO, and OH + CHCl. On the basis of this ab initio potential energy surface and the experimental rate constant at 297 K, the kinetics of the title reaction have been calculated by a “loose transition-state” model and RRKM theory. The overall rate constants can be fitted to a double-exponential formula k ( T ) = (1.51 ± 0.01) × 10 -10 exp[(1.36 ± 0.01) kJ mol -1 /( RT )] + (2.23 ± 0.09) × 10 -10 exp[(−27.48 ± 0.73) kJ mol -1 /( RT )] cm 3 molecule -1 s -1 over the temperature range 250−2000 K. The energy-specific rate constants of the unimolecular decomposition of the activated adduct OCH 2 Cl* are used to estimate the branching ratio. The production of H + CHClO is the major reaction channel, and the production of Cl + CH 2 O is the minor reaction channel.