Kinetics of the gas-phase addition reactions of trichlorosilyl radicals. Part 3.—Additions to 2-olefins

Abstract

The following Arrhenius parameters for the forward and reverse steps of trichlorosilyl radical additions to trans-but-2-ene, cis-but-2-ene, cis-pent-2-ene, 2-methyl-but-2-ene and cyclopentene have been obtained by a competitive method. The relevant elementary reactions are ·SiCl₃+ CH₃COCH₃→(CH₃)₂ĊOSiCl₃(3), ·SiCl₃+CC⇌Ċ—[graphic omitted]—SiCl₃(5, –5), and —[graphic omitted]—SiCl₃+ HSiCl₃→ H[graphic omitted]—[graphic omitted]SiCl₃+·SiCl₃(6), [graphic omitted].

The rate parameters of reaction (5) are expressed per reaction site; an asterisk indicates the site of addition in an unsymmetrical olefin. Evaluated values of A_–5 and A₅ imply a fairly ‘loose’ transition state in reaction (5). The Si—C bond energy has been estimated. ·SiCl₃ radicals have been revealed to be electrophilic and susceptible to steric hindrance.