Ab initio calculations at different levels of theory and using several basis sets were performed for the title two-channel hydrogen-abstraction reaction. Conclusions are drawn from G2 energies. These calculations have shown that this reaction, which can give two products (namely, CH3O and CH2OH), proceeds through the formation of intermediate complexes followed by transition states with quite negligible activation energy. We propose a method for the calculation of the rate constant of a bimolecular reaction proceeding through the formation of two intermediate complexes. General equations, taking into account the rotational energy, are derived from RRKM theory, using the simplified version of the SACM theory. The resulting calculated overall rate constant as well as the yield of the methoxy branching ratio are in very good agreement with experimental findings. The expressions for the site-specific rate constants k(CH3O) and k(CH2OH) allow the description of the reaction kinetics over a wide range of temperatures. A temperature rate constant fit, convenient for chemical modeling studies, is k(CH3O) = 1.0 × 10-10 (T/300)0.5 cm3 molecule-1 s-1 and k(CH2OH) = 6.9 × 10-11 (T/300)0.27 cm3 molecule-1 s-1.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry