过氧化氢与苯乙烯环氧化的反应机理及溶剂效应

Reaction Mechanism and Solvent Effects of Styrene Epoxidation with Hydrogen Peroxide

以过氧化氢与苯乙烯环氧化为模型反应,采用Materials Studio软件中Dmol3模块,模拟计算了过氧化氢与苯乙烯的环氧化反应机理.并用连续介质-类导体屏蔽模型(COSMO)研究了反应体系分别在三种质子性溶剂(水,乙醇,叔丁醇)中的溶剂化效应.为研究溶剂分子直接参与反应的微观过程,用离散介质模型模拟了单个水分子、乙醇分子和叔丁醇分子分别对反应的影响.两种溶剂模型所得的结果一致,叔丁醇作溶剂时反应活性最好,乙醇次之;质子性溶剂能够促进过氧化氢分子的异裂,形成活性氧物种,从而使反应能垒降低.

In this paper,styrene epoxidation with hydrogen peroxide was used as a model reaction.The Dmol3 implementation in the Materials Studio Software was used to simulate the mechanism of the model reaction.Solvent effects in the reaction were also studied using the conductor-like screening model（COSMO） as a part of the continuum model in three solvents：water,ethanol,and tert-butyl alcohol.To investigate the micro-process wherein the solvent molecules react with the solute molecules directly,the discrete model was employed to simulate the impact of a single molecule of water,ethanol and tert-butyl alcohol on the reaction.Consistent results were obtained for the two different solvent models.Reaction activity was most favorable for the tert-butyl alcohol followed by ethanol.Protic solvent molecules promote the heterolytic cleavage of hydrogen peroxide and form active oxygen species,which can reduce the reaction barrier.