Hydrogen Abstraction Reaction of Hydroxyl Radical with 1,1-Dibromoethane and 1,2-Dibromoethane Studied by Using Semi-Classical Transition State Theory

The hydrogen abstraction reaction by OH radical from CH2BrCH2Br (R1) and CH3CHBr2 (R2) is investigated theoretically by semiclassical transition state theory. The stationary points for both reactions are located by using ωB97X-D and KMLYP density functional methods along with cc-pVTZ basis. Single-point energy calculations are performed at the QCISD(T) and CCSD(T) levels of theory with different basis sets. The results show that the activation energies are very sensitive to the effects of electron correlation and basis set. In order to correct basis set effects on the calculated energetic, a correction factor (CF) is determined from the energy difference between the MP2/cc-pVTZ and MP2/aug-cc-pVTZ levels. xij vibrational anharmonicity coefficients, needed for semi-classical transition state theory, are calculated at the KMLYP/cc-pVTZ level of theory. Thermal rate coefficients are computed over the temperature range from 200 to 3000 K and they are shown to be in accordance with available experimental data.