Theoretical studies on the mechanisms and dynamics of OH radicals with CH(2)FCF(2)OCHF(2) and CH(2)FOCH(2)F.

The mechanisms and dynamics studies of the multichannel reactions of CH(2)FCF(2)OCHF(2) + OH (R1) and CH(2)FOCH(2)F + OH (R2) have been carried out theoretically. Three hydrogen abstraction channels and two displacement processes are found for reaction R1, whereas there are two hydrogen abstraction channels and one displacement process for reaction R2. The minimum energy paths are optimized at the B3LYP/6-311G(d,p) level, and the energy profiles are further refined by interpolated single-point energies (ISPE) method at the BMC-QCISD level of theory. By means of canonical variational transition state theory with small-curvature tunneling correction, the rate constants of reactions R1 and R2 are obtained over the temperature range of 220-2000 K. The rate constants are in good agreement with the experimental data for reaction R1 and estimated data for reaction R2. The Arrhenius expression k(1) = 1.62 x 10(-20) T(2.75) exp(-1011/T) for reaction R1 and k(2) = 3.40 x 10(-21) T(3.04) exp(-384/T) for reaction R2 over 220-2000 K are obtained. Furthermore, to further reveal the thermodynamics properties, the enthalpies of formation of reactants CH(2)FCF(2)OCHF(2), CH(2)FOCH(2)F, and the product radicals CHFCF(2)OCHF(2), CH(2)FCF(2)OCF(2), and CHFOCH(2)F are calculated by using isodesmic reactions.