DFT法研究离子液中EMIM+催化丁烯双键异构反应机理(II)

用密度泛函理论(DFT)在B3LYP/6-31G(d, p)的计算水平上研究了离子液中1-乙基-3-甲基咪唑阳离子(EMIM⁺)的4-H和5-H原子催化丁烯双键异构反应的可能途径，优化了反应体系的平衡态和过渡态的几何构型，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. 计算结果表明, 离子液中的EMIM⁺首先通过4-H和5-H原子吸附丁烯, 进而催化丁烯的双键异构反应, EMIM⁺的4-H和5-H催化1-丁烯异构为2-丁烯的正反应活化能分别为204.2和207.3 kJ•mol^-1，逆反应活化能约为220.9和223.8 kJ•mol^-1， 反应为基元反应.

DFT Studies on Reaction Mechanism of the Double Bond Isomerization of Butene Catalyzed by 1-ethyl-3-methyl-imidazolium of the Ionic Liquid (Ⅱ)

The possible reaction paths of butene isomerization catalyzed by 4-H and 5-H of 1-ethyl-3-methyl-imidazolium (EMIM⁺) have been studied by using density functional theory (DFT) at B3LYP/6-31G** levels. The geometries of the reactants, transition states and products are fully optimized by energy gradient technology and the equilibrium states and transition states are verified according to the number of imaginary frequency obtained through vibrational analysis. The computed results indicate that the butene molecule approaches to 4-H or 5-H of EMIM⁺ at the first and then forms a supermolecule due to physical adsorption. Whereafter the isomerization of butene double bond is catalytically performed. The forward energy barriers of the rearrangement reaction catalyzed by 4-H and 5-H atom of EMIM⁺ are 204.2 and 207.3 kJ•mol^-1, and the reverse energy barriers are 220.9 and 223.8 kJ•mol^-1, respectively. The isomerization of butene catalyzed by the proton of the imidazolium ring may proceed through multi-channel at one-step process.