Theoretical investigations on •Cl-initiated atmospheric degradation of CHX2O2 (X = F, Cl)

Abstract

The triplet and complex singlet potential energy surfaces (PES) of the Cl + CHX2O2 (X=F, Cl) reactions have been investigated at the BMC−CCSD//B3LYP/6-311++G(d,p) level. Addition/elimination and SN2 displacement mechanisms are revealed on the singlet PES. H-abstraction and SN2 displacement mechanisms are located on the triplet PES. Rice-Ramsperger-Kassel-Marcus (RRKM) theory and transition-state theory (TST) are employed to calculate the overall and individual rate constants over a wide range of temperatures and pressures. It is predicted that IM1X (CHX2OOCl (X=F, Cl)) formed by collisional stabilization is dominated at T≤800 K and T≤400 K, respectively; P1X (CX2O(X=F, Cl) + HClO) was the major products at 800–2800 K and 400–3000 K, respectively; and the channel of production P3F (CF2O2 + HCl) dominant the reaction at T ≥ 2800 K. The lifetimes of CHX2O2 (X=F, Cl) in the presence of Cl are predicted to around 1.17 and 2.98 weeks, respectively. Moreover, time-dependent density functional theory (TDDFT) calculations suggest that IM1X (CHX2OOCl (X=F, Cl)) will photolyze under the sunlight.