[MOBMIM][Gly]催化环氧丙烷与CO_(2)-环加成反应的机理研究  

The mechanism of the cycloaddition reaction of propylene oxide with CO_(2)catalyzed by[MOBMIM][Gly]

作　　者：姜杉 王莹 王妹 郑丹宁 JIANG Shan;WANG Ying;WANG Mei;ZHENG Danning(School of Tropical Medicine/School of Pharmacy,Hainan Medical University,Haikou 571199,Hainan,China)

机构地区：[1]海南医科大学热带医学院/药学院,海南海口571199

出　　处：《化学研究》2024年第6期517-524,共8页Chemical Research

基　　金：海南省自然科学基金项目(824QN268);海南医学院大学生创新创业训练计划项目(X202311810036)。

摘　　要：利用密度泛函理论,研究了氨基酸型离子液体1-(4-甲氧基丁基)-3-甲基咪唑甘氨酸盐([MOBMIM][Gly])催化CO_(2)与环氧丙烷(PO)的环加成反应的机理。此外,还采用前线分子轨道理论探究了催化剂与反应底物的反应性,并且结合自然键轨道(NBO)理论分析了影响氨基酸离子液体催化活性的主要因素。计算结果表明,最优反应路径为[MOBMIM][Gly]催化的三步反应机理,即环氧化合物开环、CO_(2)插入和闭环生成产物。其中开环步与闭环步的能垒相近而成为竞争步骤。虽然[MOBMIM][Gly]在催化反应体系中能够吸收CO_(2)生成氨基甲酸盐[MOBMIM][CGly],但同时也削弱了氨基酸阴离子的亲核活化能力,导致反应能垒升高,不利于PO的开环,因此[MOBMIM][CGly]成为催化剂的可能性不大。NBO分析结果表明,[Gly]-阴离子的亲核活化在促进PO开环过程中起着关键作用。The mechanism of the cycloaddition reaction of CO_(2)with propylene oxide(PO)catalyzed by the amino acid ionic liquid 1-(4-methoxybutyl)-3-methylimidazolium glycinate([MOBMIM][Gly])was investigated for the first time by utilizing density functional theory.In addition,the reactivity of the catalyst with the reaction substrate was explored using the frontier molecular orbital theory and main influence factors of the catalytic activity for the amino acid ionic liquids were analyzed in combination with the natural bond orbital(NBO)theory.The calculations show that the optimal reaction pathway is a three-step reaction mechanism catalyzed by[MOBMIM][Gly],i.e.,ring-opening of the epoxide,insertion of CO_(2)and closed-ring to generate the product.The energy barrier of the ring-opening step is similar to the energy barrier of the closed-ring step and becomes a competing step.Although[MOBMIM][Gly]is capable of absorbing CO_(2)to produce the carbamate[MOBMIM][CGly]in the catalytic reaction system,it weakens the nucleophilic activation ability of the amino acid anion,leading to an increased catalytic energy barrier,which is not beneficial to the ring-opening of PO,and it is thus infeasible that[MOBMIM][CGly]becomes a catalyst.The results of the NBO analyses indicate that nucleophilic activation of the[Gly]-anion plays a critical role in promoting the PO ring-opening process.

关 键 词：氨基酸离子液体 二氧化碳 环氧丙烷 密度泛函理论 

分 类 号：O643[理学—物理化学]