DFT法研究离子液中EMIM＋催化丁烯双键异构反应机理

利用密度泛函方法(DFT)分别在B3LYP/6-31G**和B3LYP/6-311＋＋G**的计算水平上优化了离子液体中1-乙基-3-甲基咪唑阳离子(EMIM＋)催化丁烯双键异构反应过程中的反应物、产物以及过渡态的几何构型,分析了反应过程中键参数的变化.通过振动分析对平衡态和过渡态进行了验证,并得到了零点能.通过计算内禀反应坐标(IRC),确认了对应于过渡态的反应物和产物. 计算结果表明,EMIM＋催化丁烯双键异构可以基元反应的方式一步完成,1-丁烯异构化为2-丁烯的活化能约为192 kJ?mol－1, 逆反应活化能约为208 kJ?mol－1, 可在室温或高于室温条件下进行.

DFT Studies on Reaction Mechanism of the Double Bond Isomerization of Butene Catalyzed by 1-Ethyl-3-methyl-lmidazolium of the Ionic Liquid

The geometries of reactant, product and transition state for the title reaction have been optimized using density functional theory (DFT) at the B3LYP/6-31G** and B3LYP/6-311＋＋G** levels. The equilibrium states and the transition state have been verified according to the number of imaginary frequency through vibrational analysis. The intrinsic reaction coordinates (IRC) have been traced, along which the changes of energies and geometric parameters have been analyzed. The computed results indicate that the present reaction is a one-step process, with the forward and reverse energy barriers being 192 and 208 kJ?mol－1 at the level of B3LYP/6-31G**, respectively, which means that the reaction might proceed at or above room temperature.