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DFT methods are used in calculations of geometries, energies, and frequencies for O (3P) + CH3OH reactions. CCSD(T) single-point calculations are carried out followed by extrapolation to the complete basis set (CBS) limit and inclusion of core correlation. The best estimate results of the reaction enthalpies (ΔH00) for the first (-7.1 kcal/mol), second (2.0 kcal/mol), and the third (25.8 kcal/mol) reactions path are in excellent agreement with the experimental values, i.e., -7.2 ± 0.2, 1.2 ± 1.0, and 26.0 ± 1.2 kcal/mol, respectively. Rate constants and activation energies in the range of 300–2,000 K calculated with the variational transition state theory are in good agreement with previous studies. H/D and 12C/13C kinetic isotope effects are also calculated in good agreement with available experimental data. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) geometries, vibrational frequencies, barrier heights, and reaction energies are computed for the first reactive channels of reactions involving the hydrogen atoms with CH3OH and C2H5OH. For both reactions, the density functional BB1K specially fitted to study hydrogen abstraction reactions was able to give barrier heights and reaction enthalpies at 0 K with accuracy close to 1.0 kcal/mol. The B3LYP systematically underestimate the classical barrier heights and predict reasonable values for the geometries and frequencies of CH3OH and C2H5OH. The results show that the studied DFTs have strengths and weaknesses which are somewhat complementary. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [ABSTRACT FROM AUTHOR]