Microwave-Assisted Synthesis and Spectral Identification of [Rmim]PF6 (R = p,b,c6) Ionic Liquids

Abstract

By microwave irradiation, the intermediates of imidazolium ionic liquids: 1-Butyl-3- methylimidazolium bromide ([bmim]Br), 1-propyl-3-methylimidazolium bromide ([pmim]Br), 1-hexyl-3-methylimidazolium bromide ([c₆mim]Br) were synthesized, respectively from 1-methylimidazole and organic bromide(1-bromobutane, 1-bromopropane, 1-bromohexane). The optimal technological conditions were obtained by the crossed experiment, i.e., 1-methylimidazole /organic halide (in mole): 1:1.1, temperature: 80 ºC, time: 20 min. The product yield was 90 % and more. Each of them reacted with HPF₆ for 4 h at room temperature, respectively to get hydrophobic imidazolium ionic liquids, i.e., 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim]PF₆), 1-propyl-3-methyl-imidazolium hexafluorophosphate ([pmim]PF₆), 1-hexane-3- methyl-imidazolium hexafluorophosphate ([c₆mim]PF₆). The product yield was about 50 %. Their structures were analyzed and identified by UV-vis, IR and H' NMR spectra, respectively.