水助甲酰胺-H_2O_2氧化乙烯制环氧乙烷反应机理的理论研究

Theoretical Study on the Epoxidation Reaction Mechanism between Ethene,Formamide and H_2O_2 Assisted by Water Molecule

采用MP2方法研究了甲酰胺-H2O2氧化乙烯制取环氧乙烷的反应机理.优化得到了反应物、过渡态、中间体及产物的几何构型并计算了反应势垒.研究结果表明:没有水参与时,反应需要通过四元环过渡态完成,反应势垒很高,在常温下难以进行;有水参与时,在水分子的协助下,反应可以通过六元环过渡态完成,反应势垒较低,常温下反应容易进行.

Theoretical study on the epoxidation reaction mechanism between ethene,formamide and H2O2 was carried out using MP2 methods.The optimal structures of reactants,transition states,intermediates and products were located at the MP2/6-31G（d,p） level of theory.The reaction barriers were then calculated at the MP2/6-311＋＋G（d,p） level of theory.The calculation results show that the high reaction barriers exist for the pathways where no water molecule involves,whereas for the pathways in which a water molecule involves,the low reaction barriers were found because of the formation of the six-membered ring transition state structures,indicating that both the water molecule and the six-membered ring transition state structure play a very important role in the epoxidation reaction between ethene,formamide and H2O2.