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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical Study of the Reaction Mechanism of Abstraction Reactions of Disilenes and Digermenes with Haloalkanes
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Theoretical Study of the Reaction Mechanism of Abstraction Reactions of Disilenes and Digermenes with Haloalkanes

机译：二烯和二锗烯与卤代烷的抽象反应机理的理论研究

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摘要

The potential energy surfaces for the abstraction reactions of disilenes and digermenes with carbon tetrachloride have been characterized in detail using density functional theory (B3LYP/6-311G(d)), including zero-point corrections. Ten substituted disilene and digermene species, R_2X＝XR_2 (X = Si, Ge; R = H, F, Cl, CH_3, and SiH_3), have been chosen in this work as model reactants. Of the two possible reaction paths, the Cl abstraction (path 1) and the CCl_3 abstraction (path 2), the former is found to be more favorable, with a very low activation energy and a larger exothermicity. This is in accordance with available experimental observations. The activation barriers and enthalpies of the reactions are compared to determine the relative reactivity of disilene and digermene as well as the influence of substitution on the reaction potential energy surface. Our theoretical investigations indicate that, irrespective of disilene and digermene species, the more electropositive and/or the more bulky the substituents, the lower the activation barrier and the more exothermic the haloalkane abstraction. In short, electronic as well as steric factors play a dominant role in determining the chemical reactivity of the disilene or digermene species kinetically as well as thermodynamically. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. The results obtained allow a number of predictions to be made.
机译：使用密度泛函理论（B3LYP / 6-311G（d）），包括零点校正，对二烯和二锗烯与四氯化碳的抽象反应的势能面进行了详细描述。在这项工作中，选择了十种取代的二ilene和digermene物种R_2X ＝ XR_2（X = Si，Ge; R = H，F，Cl，CH_3和SiH_3）作为模型反应物。在两个可能的反应路径中，Cl提取（路径1）和CCl_3提取（路径2）中，发现前者是更有利的，具有非常低的活化能和较大的放热性。这与现有的实验观察一致。比较反应的活化势垒和焓，以确定二烯和二烯的相对反应性以及取代对反应势能表面的影响。我们的理论研究表明，与二烯和二锗烯种类无关，取代基的电正性和/或体积越大，活化能垒越低，卤代烷烃的抽象放热越大。简而言之，电子和空间因素在动力学和热力学上决定二烯类或二烯类物质的化学反应性起主要作用。此外，基于Pross和Shaik的工作的配置混合模型用于合理化计算结果。获得的结果使得可以做出许多预测。

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