Kinetics of sec-Butylsilylene Isomerization to 2,3-Dimethylsilacyclopropane and the Decomposition and Isomerization Kinetics of 2,3-Dimethylsilacyclopropane

摘要

Silylene, generated from the thermal decomposition of silane between 643 and 689 K, reacts with 1-butene to produce n-butyl- and sec-butylsilane and cis- and trans- 2-butene. The mechanism of the reaction involves butylsilylene and silacyclo-propane intermediates. Sec-Butylsilylene isomerizes to 2,3-dimethylsilacyclopropane with an activation energy of E21 = 11.6 + or - 2.6 kcal, while the activation energy for the decomposition of 2,3-dimethylsilacyclopropane (to 2-butenes and silylene) is significantly higher than the activation energy for its back reaction to sec-butylsilylene, (E22-E-21) = 11.5 + or - 0.5 kcal. Further the decomposition of the silacyclopropane is several times faster than its isomerization, indicating a high A factor and consecutive step, biradical mechanism for the decomposition.