Computational study on mechanisms and kinetics of the atmospheric CFCl2CH2O2 with Cl reaction

Abstract

Ab initio BMC-CCSD//B3LYP calculations of the potential energy surfaces (PESs) are associated with the rate constants and branch ratio of products by means of RRKM theories to research the mechanism and product distribution of the CFCl₂CH₂O₂ with Cl reaction. The singlet and triplet PESs of this reaction have been calculated. Addition/elimination and S_N2 displacement mechanisms are located on the singlet PES, and S_N2 displacement and H-abstraction are located on the triplet PES. P1 (CFCl₂CHO + HClO) are expected to the primary products at T ≤ 2400 K, which is by original barrierless Cl addition to the terminal-O atom in CFCl₂CH₂O₂ and then eliminate HClO molecule, and the branch ratio of products rely on collision energy. The H-abstraction products on the triplet PES are the dominant products at higher temperatures. At 298 and 500 K, the total rate constants are not subject to pressure, conversely, the total rate constants presented typical falloff behavior at 1000 and 3000 K. The atmospheric lifetime of CFCl₂CH₂O₂ in Cl is around one day. TD-DFT computations imply that IM1 (CFCl₂CH₂OOCl) and IM2 (CFCl₂CH₂OClO) will photolyze under the sunlight.

Keywords: Atmospheric reaction; CFCl(2)CH(2)O(2); Cl; PES; Reaction mechanism.