物理化学学报 >> 2012, Vol. 28 >> Issue (12): 2831-2838.doi: 10.3866/PKU.WHXB201208134

理论与计算化学 上一篇    下一篇

硅苯与HX (X=F, OH, NH2)的1,2-及1,4-加成反应

王岩, 曾小兰   

  1. 信阳师范学院化学化工学院, 河南 信阳 464000
  • 收稿日期:2012-06-20 修回日期:2012-08-13 发布日期:2012-11-14
  • 通讯作者: 王岩 E-mail:wangyanxytc@163.com
  • 基金资助:

    河南省基础与前沿技术研究计划(092300410207)资助项目

1,2- and 1,4-Addition Reactions between Silabenzenes and HX (X=F, OH, NH2)

WANG Yan, ZENG Xiao-Lan   

  1. College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, Henan Province, P. R. China
  • Received:2012-06-20 Revised:2012-08-13 Published:2012-11-14
  • Supported by:

    This work was supported by Henan Provincial Fundamental and Frontier Technological Research Program, China (092300410207).

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摘要：

采用密度泛函理论方法在B3LYP/6-311++G(d,p)水平上, 研究了硅苯与HX (X=F, OH, NH2)的1,2-及1,4-加成反应的微观机理和势能剖面, 考察了Si 原子上的取代基及四氢呋喃溶剂对反应势能剖面的影响. 研究结果表明, 标题反应有两种可能的机理: (1) 硅苯与一个HX (X=F, OH, NH2)分子先形成中间复合物, 然后经过四元环过渡态(机理1)生成最终产物; (2) 硅苯与两个HX分子先形成中间复合物, 然后经过六元环过渡态(机理2)生成另一中间复合物, 该中间复合物脱去一个HX分子形成最终产物. 机理2 在动力学上远较机理1 有利. 1,2-及1,4-加成产物哪种优先形成由动力学控制且与X基团的种类有关. HX在气相中参与加成反应从易到难的次序为: HF>H2O>NH3. Si 原子上具有较强供电子和吸电子性质的取代基, 在热力学和动力学上均有利于反应的进行, 但具有较大体积的2,4,6-三甲基苯基取代基对反应反而不利. 四氢呋喃溶剂在热力学上不利于硅苯与HX的1,2-及1,4-加成反应, 在动力学上对HF或H2O作为加成试剂的反应也不利, 但对NH3作为加成试剂的反应反而有利.

关键词: 密度泛函理论, 硅苯, 加成反应, 反应机理

Abstract:

Density functional theory calculations at the B3LYP/6-311 ++ G(d,p) level were performed to study the reaction mechanism and potential energy surface of the 1,2- and 1,4-addition reactions between silabenzenes and HX (X=F, OH, NH2). The influences of substituents at the Si atom and tetrahydrofuran as a solvent on the potential energy surfaces of the reactions were also explored. The results indicated that the title reactions occur by the following two mechanisms: (1) silabenzene and one HX molecule form an intermediate complex, and then isomerize to give final product via a four-membered transition state; and (2) silabenzene and two HX molecules form an intermediate complex, and then isomerize via a sixmembered transition state to give another intermediate complex from which one HX molecule is left to afford the final product. Mechanism 2 is much more favorable than mechanism 1 kinetically. The preference for the 1,2- or 1,4-addition product is determined by kinetics and is related to the X group. The reactivity order of HX toward the addition reaction with silabenzene in gas phase is HF>H2O>NH3. Strong electron-donating and -withdrawing substituents at the Si atom have a favorable influence on the potential energy surfaces of the 1,2- and 1,4-addition reactions, while the large mesityl group has the opposite effect. Tetrahydrofuran has an unfavorable thermodynamic influence on the reactions, and kinetically on those reactions with HF or H2O. However, it favors the reactions between silabenzenes and NH3 kinetically.

Key words: Density functional theory, Silabenzene, Addition reaction, Reaction mechanism