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用密度泛函理论考察了甲基咪唑和一系列的卤代烷烃(氯乙烷,氯丁烷,溴乙烷,溴丁烷)反应合成咪唑类离子液体的反应机理.在B3LY P/6-31++G鄢鄢//B3LY P/6-31G鄢基组水平上找到了两条反应路径:路径A (反应物邛TS1邛P1)和路径B (反应物邛TS2邛P2).在路径A 中,卤素离子和咪唑环C2 上的氢质子形成氢键;在路径B 中,卤素离子和咪唑环C5 上的氢质子形成氢键.计算发现,氢键的形成在反应中起到了非常重要的作用,特别是咪唑环C2 上的氢质子在和卤素离子成氢键后形成了一个五员环结构的过渡态, 该过渡态能量较低.经过渡态TS1 的反应途径其活化能要低于经过渡态TS2 的反应途径, 反应路径A 为主要的反应通道.计算结果表明,经过渡态TS1 的反应途径是一放热过程,这和实验观察现象一致.
The mechanism of reaction of methylimidazole with a series of haloalkanes (chloroethane, chlorobutane, bromoethane, bromobutane) to synthesize imidazole ionic liquids was investigated by density functional theory. At B3LY P / 6-31 + GYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYUINDOWSYYYYYYYYYYYYYYYYYYYYYYYYYYU.Four reaction paths were found at the level of Yanji group: path A (reactant 邛 TS1 邛 P1) and path B , The hydrogen ion forms a hydrogen bond with the hydrogen proton on the imidazole ring C2 and the hydrogen ion forms a hydrogen bond with the hydrogen proton on the imidazole ring C5 in Route B. It has been found that the hydrogen bond formation plays a very important role in the reaction Especially the hydrogen protons of the imidazole ring C2 form a five-membered ring structure transition state with the hydrogen ion of the halogen ion, which has a lower energy and the activation energy of the transition state TS1 is lower than Through the reaction pathway of the transition state TS2, the reaction path A is the main reaction channel, and the calculation results show that the reaction pathway through the transition state TS1 is an exothermic process, which is consistent with the experimental observation.