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.

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