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Bimolecular Reaction Dynamics in the Phenyl - Silane System: Exploring the Prototype of a Radical Substitution Mechanism

submitted on 01.08.2018 and posted on 02.08.2018 by Michael Lucas, Aaron M. Thomas, Tao Yang, Ralf I. Kaiser, Alexander M. Mebel, Diptarka Hait, Martin Head-Gordon

We present a combined experimental and theoretical investigation of the bimolecular gas phase reaction of the phenyl radical (C6H5) with silane (SiH4) under single collision conditions to investigate the chemical dynamics of forming phenylsilane (C6H5SiH3) via a bimolecular radical substi­tu­tion mechanism at a tetra-coordinated silicon atom. Verified by electronic structure and quasiclassical trajectory calculations, the replacement of a single carbon atom in methane by silicon lowers the barrier to substi­tu­ti­on thus defying conventional wisdom that tetra-coordinated hydrides undergo preferentially hydrogen abstraction. This reaction mechanism provides funda­men­tal insights into the hitherto unexplored gas phase chemical dynamics of radical substitution reactions of mononuclear main group hydrides under single collision conditions and highlights the distinct reactivity of silicon compared to its isovalent carbon. This mechanism might be also involved in the synthesis of cyanosilane (SiH3CN) and methylsilane (CH3SiH3) probed in the circumstellar envelope of the carbon star IRC+10216.


The Hawaii group thanks the National Science Foundation (NSF) for support under award CHE-1360658. Work at Berkeley was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE- AC02-05CH11231. D.H. also acknowledges funding via a Berkeley Fellowship.


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University of California, Berkeley



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Declaration of Conflict of Interest

No conflict of interest.