...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Kinetics and Mechanism of the Addition of Aliphatic Amines to Transient Silenes
【24h】

Kinetics and Mechanism of the Addition of Aliphatic Amines to Transient Silenes

机译：脂肪族瞬态硅烷中加成胺的动力学和机理

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Primary and secondary amines such as n-butyl-, t-butyl-, and N,N-diethylamine add across the Si=C bond of transient silenes such as 1,1-diphenylsilene (1a) and 1,1-bis(4-trifluoromethylphenyl)silene (1b) to yield the corresponding amino(methyl)diarylsilanes as the only products of reaction. The kinetics and mechanism of reaction of these three amines with the two 1,1-diarylsilene derivatives have been studied in hexane, acetonitrile, and tetrahydrofuran (THF) solution by laser flash photolysis techniques, using the corresponding 1,1-diarylsilacyclobutanes as photochemical precursors to the silenes. The reactions proceed with clean second-order kinetics and bimolecular rate constants in excess of 5 * 10~8 M~(-1) s~(-1) in hexane and MeCN, with 1b being up to four times more reactive than 1a. Arrhenius plots for reaction in hexane and/or acetonitrile solution show strong curvature over the 0-60 ℃ temperature range, consistent with an addition mechanism involving the intermediacy of a zwitterionic silene-amine addition complex, which collapses to product by intramolecular proton transfer from nitrogen to the silenic carbon. The reactions are substantially slower in THF, where rate reductions on the order of 5-10-fold and 50-70-fold are observed for 1a and 1b, respectively, as compared to MeCN solution. This is due to the effects of complexation of the silenes with the ether solvent, the equilibrium constant for which enters the expression for the reaction rate constant in the complexing solvent. In contrast to the situation in hexane and MeCN, Arrhenius plots for reaction of n-BuNH_2 with 1a,b in THF solution are linear and lead to positive activation energies. Addition of amines in THF solution is proposed to occur predominantly via the free silenes but with minor contributions from a pathway involving nucleophilic displacement of the solvent from the silene-solvent complex.
机译：伯胺和仲胺（例如正丁基，叔丁基和N，N-二乙胺）通过瞬态硅（例如1,1-二苯基硅（1a）和1,1-双（4） -三氟甲基苯基）硅烷（1b）生成相应的氨基（甲基）二芳基硅烷作为唯一的反应产物。使用相应的1,1-二芳基硅环丁烷作为光化学前体，通过激光快速光解技术研究了这三种胺与两种1,1-二芳基硅衍生物在己烷，乙腈和四氢呋喃（THF）溶液中的反应动力学和反应机理。到硅烷。反应以纯净的二级动力学和双分子速率常数进行，在己烷和MeCN中的双分子速率常数超过5 * 10〜8 M〜（-1）s〜（-1），其中1b的反应活性是1a的四倍。在0-60℃温度范围内，在己烷和/或乙腈溶液中反应的阿累尼乌斯曲线显示出很强的曲率，这与两性离子硅-胺加成配合物的中间加成机理相符，该结构通过氮的分子内质子转移而分解成产物到希利尼克碳。反应在THF中明显较慢，与MeCN溶液相比，其中1a和1b分别观察到速率降低约5-10倍和50-70倍。这归因于硅烷与醚溶剂的络合作用，该平衡常数成为络合溶剂中反应速率常数的表达式。与己烷和MeCN的情况相反，n-BuNH_2与1a，b在THF溶液中反应的Arrhenius图是线性的，并导致正活化能。提出胺在THF溶液中的添加主要通过游离的硅烯进行，但是来自涉及溶剂从硅烯-溶剂络合物的亲核取代的途径的贡献很小。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号