Mechanistic and kinetic study on the reaction of the•Cl-initiated atmospheric degradation of CFCl2O2

The gas-phase reaction between CFCl(2)O(2)and Cl was researched by means of quantum chemical methods. B3LYP method with the 6-311++G(d,p) basis set were employed to obtain the geometrical parameters of all stationary points including in the reaction. The singlet and triplet potential energy surfaces (PESs) were characterized at the Multicoefficient Correlation Method (BMC-CCSD)//B3LYP/6-311++G(d,p) level. Addition/elimination and S(N)2 displacement reaction mechanisms were identified on the singlet PES, and only S(N)2 displacement reaction mechanism was located on the triplet PES. The dominant reaction takes place on the singlet PES, and the primary pathways are CFCl2O2+ Cl -> IM1 (CFCl2OOCl) -> P1 (ClClO + CFClO) and CFCl2O2+ Cl -> IM1 (CFCl2OOCl) -> IM3 (CFCl (OCl)(2)) -> P2 (ClOCl + CFClO). Rice-Ramsperger-Kassel-Marcus (RRKM) theory was used to calculate rate constants, which is consistent with the experimental data. The atmospheric lifetime of CFCl(2)O(2)in Cl is about 4.9 h in the marine boundary layer. Time dependent density functional theory (TDDFT) computations imply that IM1 (CFCl2OOCl), IM2 (CFCl2OClO), IM3 (CFCl (OCl)(2)), IM4 (FOCCl2OCl) will photolyze under the sunlight.