Theoretical investigation of the O(P-3)+CHX2 (X = F, Cl) reactions

The reactions of oxygen atoms with the CHX2 (X = F, Cl) radicals have been studied for the first time using the G2(MP2) method. The extensive calculat ions reveal the capture-limited association-elimination mechanism for the O + CHX2 reaction. For the O(P-3) + CHF2 reaction, two energy-rich intermedi ates, CHF2O* and CF2OH*, are formed along the reaction path. CHF2O* has fou r unimolecular production channels: H + CF2O; CF2OH; F + CHFO; and HF + FCO . The isomer CF2OH Can decompose to H + CF2O, HF + FCO, OH + CF2, and F + F COH. The analogous production channels such as Cl + CHClO, H + CCl2O, HCl ClCO, OH + CCl2, and Cl + ClCOH are investigated for the O(P-3) + CHCl2 re action. It should be noted that three-center direct elimination of HCl from the adduct CHCl2O* was characterized using the semiempirical AM1 method. O n the basis of the ab initio potential energy surfaces, the kinetics and th e dynamics for these two atom/radical reactions are discussed qualitatively . For the O + CHF2 reaction, H and CF2O are predicted to be the major produ cts. For the O(P-3) + CHCl2 reaction, the major production channel is the f ormation of Cl + CHClO, while the HCl + ClCO channel may be competitive.