Addition-Elimination or Nucleophilic Substitution? Understanding the Energy Profiles for the Reaction of Chalcogenolates with Dichalcogenides
Addition-Elimination or Nucleophilic Substitution? Understanding the Energy Profiles for the Reaction of Chalcogenolates with Dichalcogenides
复制标题
DOI：
10.1021/acs.jctc.6b00253
复制
发表时间：
2016-06-01
影响因子：
5.5
通讯作者：
Bickelhaupt, F. Matthias
中科院分区：
文献类型：
--
作者：
Bortoli, Marco;Wolters, Lando P.;Bickelhaupt, F. Matthias
我们用相对论密度泛函理论在ZORA-OLYP/TZ2P和COSMO上对CH3X-与CH3X‘X’CH3(X，X‘，X’‘=S，Se，Te)的取代反应机理进行了量子化学研究，模拟了水溶剂化效应。在气相中，所有的取代反应都通过包含稳定的三中心中间体的三势垒加成-消除机制进行。在某些情况下，水溶剂化使反应的性质转变为双势垒S(N)2，其中稳定的三中心中间体变成了不稳定的过渡态。我们使用活化应变模型(ASM)对这些基本反应的反应性趋势和一些令人费解的方面，特别是活化能的消失和幽灵三中心中间体进行了合理化。
We have quantum chemically explored the mechanism of the substitution reaction between CH3X- and the homo- and heterodichalcogenides CH3X'X '' CH3 (X, X', X '' = S, Se, Te) using relativistic density functional theory at ZORA-OLYP/TZ2P and COSMO for simulating the effect of aqueous solvation. In the gas phase, all substitution reactions proceed via a triple-well additionelimination mechanism that involves a stable three-center intermediate. Aqueous solvation, in some cases, switches the character of the mechanism to double-well S(N)2 in which the stable three-center intermediate has become a labile transition state. We rationalize reactivity trends and some puzzling aspects of these elementary reactions, in particular, vanishing activation energies and ghost three-center intermediates, using the activation strain model (ASM).