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.