Theoretical study on the kinetics for OH reactions with CH3OH and C2H5OH

Kinetics and mechanisms for reactions of OH with methanol and ethanol have been investigated at the CCSD(T)/6-311 + G(3df, 2p)//MP2/6-311 + G(3df, 2p) level of theory. The total and individual rate constants, and product branching ratios for the reactions have been computed in the temperature range 200–3000 K with variational transition state theory by including the effects of multiple reflections above the wells of their pre-reaction complexes, quantum-mechanical tunneling and hindered internal rotations. The predicted results can be represented by the expressions k1 = 4.65 × 10−20 × T2.68 exp(414/T) and k2 = 9.11 × 10−20 × T2.58 exp(748/T) cm3 molecule−1 s−1 for the CH3OH and C2H5OH reactions, respectively. These results are in reasonable agreements with available experimental data except that of OH + C2H5OH in the high temperature range. The former reaction produces 96–89% of the H2O + CH2OH products, whereas the latter process produces 98–70% of H2O + CH3CHOH and 2–21% of the H2O + CH2CH2OH products in the temperature range computed (200–3000 K).