Dissociation and thermochemistry of methylsilanitrile and silylsilanitrile: implications for the chemistry of silicon in interstellar medium

Abstract

Dissociation and thermochemistry of CH₃SiN and SiH₃SiN have been studied in detail using high level quantum chemical methods. The enthalpy of formation of these molecules at 0 K and 298.15 K are predicted by G3 and G3//B3LYP methods using an atomization scheme. The bond dissociation energy and energy barrier for the dissociation pathways are estimated at 0 K and the most energetically favourable dissociation products are predicted for the thermal decomposition reactions of the species in the gas phase. Finally, the enthalpy of dissociation for the most energetically favourable channel is calculated at 298.15 K. Among the four dissociation channels of CH₃SiN, the most energetically favourable is SiN(²∑⁺) + CH₃() having dissociation energy 57.4 kcal/mol. For SiH₃SiN, dissociation channel SiN(²∑⁺) + SiH₃() is the most energetically favourable, and its dissociation energy is about 1.4 kcal/mol higher than that of CH₃SiN. The most energetically favourable dissociation channels may be a potential source of SiN radical in the interstellar medium.

Keywords:

• methylsilanitrile
• silylsilanitrile
• ab initio
• DFT
• thermodynamics
• dissociation energetics

Acknowledgements

B. Mondal is grateful to the Council of Scientific and Industrial Research (CSIR), Govt. of India for awarding him a Junior Research Fellowship. Thanks are also due to the reviewer for his constructive comments to improve the paper.