Green Chemistry with a Novel 5.8-GHz Microwave Apparatus. Prompt One-Pot Solvent-Free Synthesis of a Major Ionic Liquid: The 1-Butyl-3-methylimidazolium Tetrafluoroborate System

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• 作者：Satoshi Horikoshi ; Tomofumi Hamamura ; Masatsugu Kajitani ; Masahiro Yoshizawa-Fujita ; Nick Serpone
• 刊名：Organic Process Research & Development
• 出版年：2008
• 出版时间：November 21, 2008
• 年：2008
• 卷：12
• 期：6
• 页码：1089-1093
• 全文大小：220K
• 年卷期：v.12,no.6(November 21, 2008)
• ISSN：1520-586X

文摘

This article reports for the first time the rapid one-pot solvent-free synthesis of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF₄), a major ionic liquid, in good yields (87%) after 30 min of microwave irradiation with microwaves at a frequency of 5.8 GHz in a batch-mode reactor. By contrast, the yields of [bmim]BF₄ are about 3-to-4-fold smaller when using 2.45-GHz microwave radiation and oil bath heating: 28% and 21%, respectively, under otherwise identical conditions. This further shows the advantage(s) of the 5.8-GHz microwave radiation and the accompanying apparatus as a novel synthetic tool reported in some detail elsewhere {Org. Process Res. Dev.. 2008, 12, 257−263}. The three synthetic methods (viz., 5.8-GHz and 2.45-GHz microwave heating, and oil bath heating) were examined in reactors used in both the batch and reflux modes. In the latter mode, the yields of [bmim]BF₄ were less than 10% even after a 60-min reaction period. The dependence of the synthesis on the frequency of the microwave radiation is discussed in terms of the chemical yields of the product and the dielectric factors of each substrate in the synthesis mixtures composed of 1-methylimidazole, 1-chlorobutane, and sodium tetrafluoroborate.