Theoretical Studies of the Reactions of CF3CHClOCHF2/CF3CHFOCHF2 with OH Radical and Cl Atom And Their Product Radicals with OH

The mechanisms and dynamics Studies of the OH radical and Cl atom with CF3CHClOCHF2 and CF3CHFOCHF2 have been carried out theoretically. The geometries and frequencies of all the stationary points a e optimized at the B3LYP/6-311G(d.p) level, and the energy profiles are further relined by interpolated single-point energies (ISPE) method at the G3(MP2) level of theory. For each reaction, two H-abstraction channels are found and four products (CF3CHFOCF2, CF3CFOCHF2, and CF3CHClOCF2, CF3CClOCHF2) are produced during the above processes. The rate constants for the CF3CHClOCHF2/CF3CHFOCHF2 + OH/Cl reactions are calculated by canonical variational transition-state theory (CVT) within 200-2000 K, and the small-curvature tunneling is included. The total rate constants calculated from the sum of the individual rate constants and the branching ratios are in good agreement with the experimental data. The Arrhenius expressions for the reactions are obtained. Our calculation shows that the substitution of Cl by F decreases the reactivity of CF3CHClOCHF2 toward OH and Cl. In addition. the mechanisms Of Subsequent reactions of product radicals and OH radical are further investigated at the G3(MP2)//B3LYP/6-311G(d,p) level, and the main products are predicted in the this article. (C) 2008 Wiley Periodicals. Inc. J Comput Chem 30: 565-580, 2009