Theoretical investigations on mechanisms and kinetics of CH2XO2 (X=F, Cl) with Cl reaction in the atmosphere.

Abstract

The reactions of the CH2XO2 (X=F, Cl) with chlorine radical have been firstly investigated utilizing the BMC-CCSD//B3LYP method. The comprehensive calculations indicate that the association-elimination and SN2 displacement reaction mechanisms existed on the singlet potential energy surface (PES), and H-abstraction and SN2 displacement reaction mechanism existed on the triplet PES for the CH2XO2 (X=F, Cl) + Cl reactions. On the triplet PES, the dominant reactions are production of P3X (CHXO2 (X=F, Cl) + HCl) by direct H-abstraction. On the singlet PES, three energy-rich adducts, IM1X (CH2XOOCl (X=F, Cl)), IM2X (CH2XOClO (X=F, Cl)), and IM3X (CH2(OX)OCl (X=F, Cl)), are produced. RRKM-computed reveals that IM1X (CH2XOOCl (X=F, Cl)) produced by collisional stabilization occupied the reaction T ≤ 500 and 400K, respectively, while P1X (CHXO (X=F, Cl) + HOCl) are forecasted to be the dominant products at high temperatures. The atmospheric lifetime of CH2FO2 and CH2ClO2 in Cl is around 1.18 and 2.50weeks, respectively. Time-dependent density functional theory (TDDFT) computations imply that IM1X (CH2XOOCl (X=F, Cl)) will photolyze under the sunlight. The current results could guide us to well understand the mechanism of the CH2XO2 (X=F, Cl) + Cl reactions and may be helpful to understand Cl-combustion chemistry. Graphical Abstract Predicted rate constant of the dominant pathways and the total rate constants at 760 Torr, N2 in the temperature region of 200-3000 K for the CH2XO2 (X=F, Cl) + Cl reactions.