Kinetics and Mechanisms of the Hydrogen Abstraction Reactions of CF3CF2CH2CH2F and CF3CH2CH2CF3 with Hydroxyl Radicals: Theoretical Studies

The mechanisms and kinetics of the hydrogen abstraction reactions from two structural isomers, CF 3 CF3CF2CH2CH2F and CF3CH2CH2CF3 (HFC-356mff), by OH radicals are investigated by quantum chemical methods along with SCTST theory. The structures of the reactants, transition states, products and hydrogen-bonded complexes are optimized by the KMLYP density functional theory method. The energies of the stationary points are also evaluated by M05-2X, M06-2X and MPWB1K methods for the purpose of comparison. The computed barrier heights and the corresponding rate coefficients are slightly affected by the quantum-chemical method. The significance of the tunnel effect and vibrational anharmonicities in predicting the rate coefficients are also investigated. The present theoretical computations predicts the atmospheric lifetimes of the CF3CF2CH2CH2F and CF3CH2CH2CF3CF 3 are about 1.00 and 6.56 years, respectively.