Kinetics of gas phase addition reactions of trichlorosilyl radicals. Part 2.—Additions to 1-olefins

Abstract

Arrhenius parameters for forward and reverse steps of trichlorosilyl radical additions to propene, but-1-ene, pent-1-ene and isobutene were obtained between 406 and 524 K by a competitive method. The elementary reactions involved are ·SiCl₃+ R₁ R₂ CCH₂→ R₁ R₂ĊCH₂SiCl₃, (5), ·SiCl₃+ CH₃COCH₃→(CH₃)₂ĊOSiCl₃(3) and R₁ R₂ĊCH₃SiCl₃+ HSiCl₃→ R₁ R₂ CHCH₂SiCl₃+· SiCl₃. (6) [graphic omitted]

The values of k₅, together with the earlier value for ethene, indicate a regular increase in reactivity with double bond substitution by an alkyl group. This tendency may be interpreted as indicating the electrophilic nature of ·SiCl₃ radicals. From the values of A_–5, it is suggested that a fairly “loose” transition state may be involved in a silyl radical detachment reaction.