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

The reactions of the CHXO (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 S2 displacement reaction mechanisms existed on the singlet potential energy surface (PES), and H-abstraction and S2 displacement reaction mechanism existed on the triplet PES for the CHXO (X=F, Cl) + Cl reactions. On the triplet PES, the dominant reactions are production of P3 (CHXO (X=F, Cl) + HCl) by direct H-abstraction. On the singlet PES, three energy-rich adducts, IM1 (CHXOOCl (X=F, Cl)), IM2 (CHXOClO (X=F, Cl)), and IM3 (CH(OX)OCl (X=F, Cl)), are produced. RRKM-computed reveals that IM1 (CHXOOCl (X=F, Cl)) produced by collisional stabilization occupied the reaction T ≤ 500 and 400 K, respectively, while P1 (CHXO (X=F, Cl) + HOCl) are forecasted to be the dominant products at high temperatures. The atmospheric lifetime of CHFO and CHClO in Cl is around 1.18 and 2.50 weeks, respectively. Time-dependent density functional theory (TDDFT) computations imply that IM1 (CHXOOCl (X=F, Cl)) will photolyze under the sunlight. The current results could guide us to well understand the mechanism of the CHXO (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 CHXO (X=F, Cl) + Cl reactions.