Gemini Dicationic Acidic Ionic Liquids: Synthesis, Properties and Catalytic Applications pp. 203-226
Authors: (Yingwei Zhao, Xiaofei Liu, Zhen Li, Jing Chen, Chungu Xia, State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China)
Abstract: The sulfonic acid (-SO3H) functionalized ionic liquids have attracted much attention in the green procedure of acid-catalyzed organic reactions. Herein, we report on the synthesis and characterization of a series of novel gemini dicationic sulfonic acidfunctionalized ionic liquids based on imidazole, pyrrolidine, and morpholine, respectively. The detailed studies on the physicochemical properties of these dicationic ionic liquids showed that they are thermally stable and electrochemically inert, and possess higher density and viscosity compared with common monocationic sulfonic acid functionalized ionic liquids. They also showed noticeable hydrophilic properties and stronger acidities, which make them more efficient in catalytic reactions. The dicationic acidic ionic liquids based on pyrrolidine exhibited excellent performance in esterification, and up to 99% yield was obtained when 5 mol% of ionic liquids was used. The
imidazole-based ionic liquids mediated ZnCl2 are also good catalysts for Beckmann rearrangement of oximes. The morpholine-based ionic liquids could catalyze the selective alkylation of phenol with t-butyl alcohol and the product distribution was found related to
the acidity of the catalyst. Furthermore, all these ionic liquids could be reused for several times without appreciable loss of efficiency, exhibiting good stability.