Theoretical kinetics and thermochemistry investigations on the H‐atom abstraction reactions by H and O atoms and OH and HO2 radicals from Si−C−O‐containing species such as Si(CH3)4, Si(CH3)3(OH), Si(CH3)2(OH)2, and Si(CH3)(OH)3 have been carried out in this work. The geometry, vibrational frequencies, and hindrance potential for each species are calculated at the B3LYP/6‐31G(2df,p) level of theory with the single‐point energies calculated at the G4 level of theory. The composite methods G3 and G4 are utilized to derive enthalpies of formation at 0 K by the atomization reaction methodology. ΔHf(298 K), S(298 K), and Cp(T) are calculated by using the statistical thermodynamics method. Conventional transition state theory is used over a wide temperature range (298.15−2000 K) for H‐atom abstraction reactions by H, O, and HO2 radicals from the species mentioned above, and variational transition state theory is used for H‐atom abstraction reactions by the OH radical. The kinetic and thermodynamic parameters based on high‐level theoretical calculations are compared with the literature data. Reactivity comparison between the similar hydrocarbons and silicon‐organic compounds for H‐atom abstractions is explored. A large difference exists between these two different systems when H‐atom abstractions are on hydroxyl sites.

An extensive and reliable database of the thermodynamic properties of C6–C12 aromatic molecules is constructed by using quantum chemistry calculations.