New dense fluoroalkyl-substituted imidazolium ionic liquids

Abstract

New mono and polyfluoroalkyl-substituted ionic liquids have been synthesized and characterized. The neat reaction of 1-methylimidazole (1a) with 1,1,1-trifluoro-3-iodopropane (2a) at 80°C formed the quaternary salt, 1-methyl-3-trifluoropropylimidazolium iodide (3), in 90% yield. Similarly, sodium imidazole (1b) gave good yields of the quaternary salts, 1,3-bis(trifluoropropyl)imidazolium iodide (3b) with an excess of 2a, and 1,3-bis(monofluoropropyl)imidazolium bromide (3c) with an excess of 1-fluoro-3-bromopropane (2b). In water as solvent, metathesis reactions of 3 with KPF6, LiN(SO2CF3)2 and KSO3CF3, and of 3b and 3c with KPF6 and LiN(SO2CF3)2 led to 4a-c, 4d,e, and 4f,g, respectively, in good isolated yields. Some of the di(polyfluoroalkyl)imidazolium salts are liquids with densities in excess of 1.8 g/cm3. © 2002 Elsevier Science Ltd. All rights reserved.