Department of Chemistry, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
J Mass Spectrom. 2010 Feb;45(2):215-22. doi: 10.1002/jms.1712.
The decomposition of 1,1-dimethyl-1-silacyclobutane (DMSCB) on a heated tungsten filament has been studied using vacuum ultraviolet laser single photon ionization time-of-flight mass spectrometry. It is found that the decomposition of DMSCB on the W filament to form ethene and 1,1-dimethylsilene is a catalytic process. In addition, two other decomposition channels exist to produce methyl radicals via the Si-CH(3) bond cleavage and to form propene (or cyclopropane)/dimethylsilylene. It has been demonstrated that both the formation of ethene and that of propene are stepwise processes initiated by the cleavage of a ring C-C bond and a ring Si-C bond, respectively, to form diradical intermediates, followed by the breaking of the remaining central bonds in the diradicals. The formation of ethene via an initial cleavage of a ring C-C bond is dominant over that of propene via an initial cleavage of a ring Si-C bond. When the collision-free condition is voided, secondary reactions in the gas-phase produce various methyl-substituted 1,3-disilacyclobutane molecules. The dominant of all is found to be 1,1,3,3-tetramethyl-1,3-disilacyclobutane originated from the dimerization of 1,1-dimethylsilene.
采用真空紫外激光单光子电离飞行时间质谱研究了 1,1-二甲基-1-硅杂环丁烷（DMSCB）在加热钨丝上的分解。研究发现，DMSCB 在 W 灯丝上分解为乙烯和 1,1-二甲基硅烯是一个催化过程。此外，还存在另外两种分解途径，通过 Si-CH(3) 键的断裂生成甲基自由基，并形成丙烯（或环丙烷）/二甲基硅烯。研究表明，乙烯和丙烯的形成都是通过分别断裂环 C-C 键和环 Si-C 键，形成双自由基中间体，然后再断裂双自由基中剩余的中心键的逐步过程。通过初始的环 C-C 键断裂形成乙烯的过程比通过初始的环 Si-C 键断裂形成丙烯的过程更为有利。当不存在无碰撞条件时，气相中的次级反应会产生各种甲基取代的 1,3-二硅杂环丁烷分子。其中最主要的是 1,1,3,3-四甲基-1,3-二硅杂环丁烷，它来源于 1,1-二甲基硅烯的二聚反应。
