Thermochemistry of organosilane compounds and organosilyl radicals

Abstract Si–C–H-containing radicals and stable species are present in the oxidation of silicon-organic compounds such as methyl and ethyl silanes, which are frequently-used precursors for the synthesis of silicon-based nanoparticles and coatings via combustion processes. Silicon-containing intermediates interact with flame radicals and thus play a major role in flame chemistry and influence flame propagation. Mechanistic understanding of these effects is hampered by very limited thermochemical properties available for relevant organosilane species. This paper presents quantum-chemical calculations and isodesmic reaction schemes for the determination of temperature-dependent heat of formation, entropy, and heat capacity of Si–C–H radicals and molecules, from which group additivity values (GAVs) were obtained from combinatorial considerations. The data for 22 stable Si–C–H species are revised using isodesmic reactions and the related 24 GAVs were refined by considering 19 additional stable Si–C–H species. In addition, quantum chemical calculations are made to calculate the thermochemistry of 61 radicals and used to derive 56 GAVs for Si–C–H containing radicals for the first time.