亚烷基卡宾及取代亚烷基卡宾与环硫乙烷反应的量子化学研究

用量子化学的密度泛函理论(DFT)在6-311G(d, p)水平上对亚烷基卡宾及取代亚烷基卡宾与环硫乙烷的硫转移反应机理进行了系统的研究. 用IRC对过渡态进行了确认. 并用组态混合模型讨论了反应势垒(ΔE^≠)与XYC＝C的单-三态能量差ΔE_ST之间的关系. 结果表明, 取代基的电负性是控制反应的主要因素, 取代基的电负性越大, 取代基越多, π电子给予体越多, 单-三态能量差ΔE_ST就越小, 该反应的活化能就越小, 反应越容易发生. 同时还讨论了该反应中环硫乙烷的C—S键的解离过程. 并与标题化合物和环氧乙烷的氧转移反应进行了比较.

Quantum Chemical Study on the Abstraction Reaction of Alkylidenecarbene and Its Substituted Species with Thiirane

The mechanisms of the abstraction reactions of alkylidenecarbenes have been characterized in detail using density functional theory. All the stationary points were determined at the B3LYP/6-311G(d, p) level of the theory. The transition states both to the reactants and the product direction in the reaction paths were examined by using the intrinsic reaction coordinate. A configuration mixing model based on the work of Pross and Shaik was used to rationalize the computational results. The results show that the electro negativity of the substituents played an important role in predicting its activity for the abstraction reactions. The major conclusion was that the stronger the π-donation or the more electro negativity the substituents, the smaller the ΔE_ST of XYC＝C and the lower the activation energy for the abstraction reactions. In other words, it is the electronic factors, rather than the steric factors, that play a decisive role in the chemistry of the alkylidenecarbene species. Furthermore, a comparison with oxirane also led to the same result.