Atmospheric chemistry of CFCl2O2: a theoretical study on mechanisms and kinetics of the CFCl2O2 + ClO reaction

The gas-phase reaction between CFCl2O2 and ClO was researched by means of quantum chemical methods. B3LYP method with the 6-311++G(d,p) basis set was used to obtain the geometric parameters of all stationary points including in the CFCl2O2 + ClO reaction. The singlet and triplet potential energy surfaces were characterized at the CCSD(T)/6-311++G(2d,2p)//B3LYP/6-311++G(d,p) level. Addition/elimination and SN2 displacement reaction mechanisms were identified on the singlet PES, and only substituent reaction mechanism was located on the triplet PES. The dominant reaction takes place on the singlet PES, and the major pathways are CFCl2O2 + ClO → IM1 (CFCl2OOOCl) → IM2 (CFCl2OOClO) → IM3 (CH3OClO2) → P6 (CFClO + (ClO)2). RRKM theory was used to calculate rate constants, which is consistent with the experimental data. The atmospheric lifetime of CFCl2O2 in ClO is around 8.84 h. TD-DFT computations imply that IM1 (CFCl2OOOCl), IM2 (CFCl2OOClO), and IM3 (CFCl2OClO2) will photolyze under the sunlight.