Theoretical investigations on mechanisms and pathways of CH2FO2/CHF2O2 with ClO reactions in the atmosphere

Abstract

The kinetics and mechanisms of the CH2FO2/CHF2O2 with ClO reactions have been investigated firstly by using the quantum chemical method. The single and triplet potential energy surfaces (PESs) of these two reactions have been obtained by using the BMC−CCSD method based on the geometries obtained at the B3LYP/6−311++G(d,p) level. For the CH2FO2 with ClO reaction, three activated intermediates, IM1 (CH2FOOOCl), IM2 (CH2FOOClO), and IM3 (CH2FOClO2) are generated along the reaction path, and then dissociate to various products. The similar production pathways are investigated for the CHF2O2 with ClO reaction. It should be noted that the isomerization of IM3 (CH2FOClO2) and the 1,3-Cl shift from IM1 (CH2FOOOCl) pathways were not found for the CH2FO2 with ClO reaction. The rate constants for the dominant product pathways are predicted by RRKM-TST theories. The major production pathway is the generation of IM1 (CH2FOOOCl)/IM1 (CHF2OOOCl) at 200−1200 K, and the generation of P1 (CHFO + HO2 +Cl)/P1 (CF2O + HO2 + Cl) by H-migration/elimination become dominant at higher temperatures for the CH2FO2/CHF2O2 + ClO reactions, respectively. The atmospheric lifetimes of CH2FO2 and CHF2O2 in ClO are around 11.38 and 8.65 h, respectively. Furthermore, on the basis of the analysis of the kinetics of all channels through which the addition and abstraction reactions proceed, we expect that the competitive power of reaction channels may vary with experimental conditions for the title reaction. The present study may be helpful for probing the mechanisms of the title reaction and understanding the halogen chemistry.