离子液体结合有机碱催化糠醛自缩合的分子反应机制  

Molecular Mechanism of Self-coupling of Furfural Catalyzed by Ionic Liquids Combined with Organic Base

作　　者：李婧婧 耿泽文 阳园 赵霞[2] LI Jingjing;GENG Zewen;YANG Yuan;ZHAO Xia(College of Arts and Sciences,Shanxi Agricultural University,Jinzhong 030801,China;Institute of Theoretical Chemistry,Shandong University,Jinan 250100,China)

机构地区：[1]山西农业大学文理学院,山西晋中030801 [2]山东大学理论与计算化学研究所,山东济南250100

出　　处：《青岛科技大学学报（自然科学版）》2020年第6期13-20,共8页Journal of Qingdao University of Science and Technology:Natural Science Edition

基　　金：山西省高等学校科技创新项目(2019L0377);山西农业大学博士科研启动项目(2017YJ37);山西省优秀博士来晋工作奖励资金科研项目(SXYBKY201724).

摘　　要：生物质资源作为可再生清洁能源近些年来备受关注,本研究运用密度泛函理论计算系统地阐明了噻唑基离子液体结合有机碱三乙基胺(NEt_3)催化生物质基平台分子糠醛自缩合生成燃料分子前驱体联糠醛的反应机制,并结合电荷布局以及分子轨道分析等方法明确了催化剂的构-效关系。结果表明高效的催化系统归因于催化剂与反应底物形成离域的三中心四电子键,有效地稳定了中间体和过渡态。接着探讨了取代基效应对噻唑基离子液体催化性能的影响,通过热力学和动力学分析,比较了3种离子液体催化剂催化活性的大小。计算结果证实源自离子液体的N-杂环卡宾,其亲核性和碱性是影响自缩合反应的关键因素,寻找二者的合理匹配是筛选离子液体催化剂的关键。Conversion of abundant and renewable biomass resources to high value-added chemicals caused extensive concern.Upgrading of biomass-based platform molecule furfural into C10 fuel intermediate 1,2-di(furan-2-yl)-2-hydroxyethanone(furoin)is one of them.A prospective way for the biomass conversion is the utilize of environmentally bengin and designable ionic liquids as catalysts.Choosing ionic liquid 3-phenyl-5-(2-hydroxyethyl)-4-methylthiazole chlorinated salt(AcO[TM]Cl)combined with organic base NEt3 as a representative example,the catalytic mechanism for self-condensation of furfural to furoin are systematically studied via density functional theory calculations.Analysis of molecular orbital and multi-center bond order demonstrate that the transition state and forward intermediate involved in the reaction show hydrogen-shared three-center-four-electron(3c-4e)bonds between substrate and NEt3,which stabilize the relative structures and hence reduce the free energy barriers.In addition,substituent effects are also taken into account by the analyses of kinetic and thermodynamic properties of three ionic liquid catalysts.The present work confirms that the nucleophilicity and basicity of NHC are important factors to control the self-coupling reaction.

关 键 词：噻唑基离子液体 糠醛 液体燃料 反应机理 密度泛函理论 

分 类 号：O643[理学—物理化学]