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 k(1) = 4.65 x 10(-20) x T-2.68 exp(414/T) and k(2) = 9.11 x 10(-20) x T-2.58 exp(748/T) cm(3) 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). (C) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.