Theoretical study on the kinetics and thermodynamics of H‐atom abstractions from tetramethylsilane‐related species

Abstract

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.

Are Si–C bonds formed in the environment and/or in technical microbiological systems?

“…If alternatively set 2, 3, 4, or 5 is used, reaction ( 1 ) turns out to be endothermic by 91, 31, 58–137, or 82 kJ/mol, respectively. Set 6 is the result of recent high-level ab initio calculations (Zhu and Zhou 2022 ); using these numbers, reaction ( 1 ) is endothermic by 86 kJ/mol. According to all these six sets, this hypothetical reaction is more or less endothermic and therefore not very likely to occur spontaneously or under catalysis to a reasonable extent.…”

“… a Tansel and Surita ( 2014 ), referencing Wilbraham et al ( 2008 ) b Riedel and Janiak ( 2022 ) c Clayden et al ( 2012 ) d Brook ( 2000 ) e Sarai et al ( 2021 ) f Zhu and Zhou ( 2022 ) g Taken from sets 1 and 2, since not available in sets 3–5 …”