Synthesis and Characterization of Alkyl Imidazolium-based Ionic Liquids

The alkyl imidazolium-based ionic liquids, 1-n-butyl-3-methylimidazole methyl carbonate ([n-BMIM]OCO2Me]) and 1,2-dimethyl-3-ethylimidazole ethyl carbonate ([EMMIM]OCO2Et]), were synthesized from N-methylimidazole, 1,2-dimethylimidazole and carbonates. Reacting with HBF4 and HPF6 at room temperature, [n-BMIM]OCO2Me] and [EMMIM]OCO2Et] were converted into four ionic liquids: 1-n-butyl-3-methylimidazolium tetrafluoroborate ([n-BMIM]BF4]), 1-n-butyl-3-methylimidazolium hexafluorophosphate ([n-BMIM]PF6]), 1,2-dimethyl-3-ethylimidazolium tetrafluoroborate ([EMMIM]BF4), and 1,2-dimethyl-3-ethylimidazolium hexafluorophosphate ([EMMIM]PF6). The six ionic liquids were characterized and analysed by FT-IR, 1H-NMR, ESI-MS and DSC. Environmental pollution was avoided by the green chemical synthetic method in comparison with the traditional two-step synthesis.