19469-02-4Relevant articles and documents
Absolute Rate Constants for Some Intermolecular and Intramolecular Reactions of α-, β-, and γ-Silicon-Substituted Radicals
Wilt, James W.,Lusztyk, J.,Peeran, Mehoob,Ingold, K. U.
, p. 281 - 287 (2007/10/02)
Rate constants for hydrogen atom abstraction from n-Bu3GeH (kGeH) by Me3SiCH2. (1.), Me3SiCH2CH2. (2.), and Me3SiCH2CH2CH2. (3.) and from n-Bu3SnH (kSnH) by 1. and 3. have been determined at ambient temperatures.The order of decreasing radical reactivity is 1. > n-alkyl > 3. > 2..However, for bromine abstraction from the parent bromides by n-Bu3Sn. and n-Bu3Ge., the order of decreasing reactivity is 1-Br > 2-Br > 3-Br ca. n-alkyl bromide.The Arrhenius equations for reaction of 1. and 3. with n-Bu3SnH were also determined: log (kSnH(1.)/(M-1 s-1)) = (10.2 +/- 0.5) - (3.90 +/- 0.62)/Θ and log (kSnH(3.)/(M-1 s-1)) = (8.4 +/- 0.7) - (2.81 +/- 0.95)/Θ, where Θ = 2.3RT kcal/mol.These kinetic data are discussed in relation to previously measured rate constant ratios, kc5+6/kSnH and kexo5/kendo6, where kc5+6 corresponds to the cyclization of α-, β-, and γ-dimethylsilyl-substituted 5-hexenyl radicals to form 5-membered (kexo5) and 6-membered (kendo6) silacycloalkylmethyl radicals.
