Computational Study on OH Radical Reaction with CHF2CHFCHF2(HFC-245ea) between 200 and 400 K

摘要

The rate coefficients of the CHF2CHFCHF2 (HFC-245ea) + OH reaction were computed using G3B3 theory in the temperature range 200 and 400 K. Geometries were optimized for all reactants, transition states, and products at the B3LYP level of theory using 6-31G~* and 6-311++G~** basis sets. Three rotamers (R1, R2, and R3) of CHF2CHFCHF2 were identified using a potential energy surface scan. Thirteen independent transition states were identified and confirmed by intrinsic reaction coordinate calculations. The kinetic parameters due to all different transition states are presented in this paper. All the three rotamers were taken into account in computing the rate coefficients. Throughout the temperature range of this study, rotamer R3 contributes significantly (more than 90%), whereas the other two rotamers R1 and R2 contribute less to the total rate coefficient. The rate coefficients for the title reaction were computed to be k = (1.86 ± 0.17) × 10~(13) exp[-(748±26)/T] cm~3molecule~(-1)s~(-1) and (1.25 ± 0.23) × 10~(13) exp(—(587 ± 50)/T ] cm~3molecule~(-1) s~(-1) with Wigner's and Eckart's unsymmetrical tunneling methods, respectively, and they are in reasonable agreement with the experimentally measured ones.