Thermophysical Properties of Imidazolium-Based Ionic Liquids: The Effect of Aliphatic versus Aromatic Functionality

Abstract

Synthesis of 1-(cyclohexylmethyl)-3-methyl imidazolium bis[(trifluoromethane)sulfonyl]amide ([CyhmC 1 im][NTf 2 ])A one-neck round bottom flask, under nitrogen, equipped with a magnetic stirrer and a condenser, was charged with 1-methylimidazole (6.65 g, 81.02 mmol). To this mixture, an excess (1.05 eq.) of (bromomethyl)cyclohexane (15.06 g, 85.07 mmol) was added. The reaction was left under constant stirring at 50 °C, until complete consumption of the 1-methylimidazole.The 1-(cyclohexylmethyl)-3-methylimidazolium bromide formed was then washed three times with 50 mL mixture of hexanes: dichloromethane (4:1 v/v) to remove the unreacted excess of halide. The product was concentrated in vacuo on a rotary evaporator. 3 g of activated charcoal and 60 mL of dichloromethane were added to the viscous, colored bromide, and left under stirring for 96 h. The black slurry was then filtered through a gravitational column packed with 10 cm of aluminum oxide (activated, basic, 50-200 micron) and 3 cm of celite 545. The removal of the solvent under reduced pressure afforded [CyhmC 1 im][Br] as a colorless, viscous liquid at room temperature. The second stage of synthesis was accomplished via a metathesis reaction. 1 An aqueous solution of lithium bis[(trifluoromethane)sulfonyl]amide (0.98 eq., 20.65 g, 71.91 mmol) was added to the [CyhmC 1 im][Br] and left to stir overnight. The two-phase system was then repeatedly washed with triple-deionized water until no bromide ions could be detected by the silver nitrate test. The final product, [CyhmC 1 im][NTf 2 ], a colorless liquid at room temperature, was dried with benzene azeotrope. The residual benzene was removed under vacuum. Yield: 91%.

Cholinium-amino acid based ionic liquids: a new method of synthesis and physico-chemical characterization

“…Similar results were also obtained by Tao et al who observed that in imidazolium based ILs the presence of the cycloalkyl group in place of the n-alkyl group with the same number of carbons leads 75to an increase in density 49. This confirms that this AA anion…”

“…We think that the insertion of the amino group in the ring structure constrains the alkyl portion in such a way that it cannot form well separated hydrophobic domains as observed for alkyl chains. 39 49 The authors concluded that the density trend could be roughly related to the C/H ratio in the substituents, with density increasing with increasing C/H ratio from n-alkyl, cycloalkyl, to aromatic functionalities. Stacking interactions could also 15 contribute to the packing of the phenyl substituents and, eventually, to their segregation in hydrophobic domains decreasing the density.…”

Physicochemical properties of piperidinium, ammonium, pyrrolidinium and morpholinium cations based ionic liquids paired with bis(trifluoromethylsulfonyl)imide anion

“…Most studies on physical properties at various temperatures have focused on imidazolium cations [18,21,22], other families of cations have been less extensively studied. In particular reports on the physicochemical properties of morpholinium based ILs are scarce [23,24].…”

Volumetric properties of 1-butyl-3-methylimidazolium bromide in aqueous solutions of d(−)-ribose and d(−)-arabinose at different temperatures

“…The synthesized IL was characterized by 1 H NMR, 13 C NMR and FTIR spectroscopic techniques. The 1 H NMR and 13 C NMR of synthesized IL were recorded on Brukar Avance 500 MHz spectrometer using CDCl 3 as solvent and TMS as the internal standard.…”

“…One of the most extensively studied class of ionic liquids are those based on imidazolium cation [5,[13][14][15][16][17][18]. In 2002, Swatloski et al [14] used imidazolium based IL for the dissolution of cellulose, since then the use of ILs particularly imidazolium based ILs for the biomass dissolution and conversion of biomass to biocompatible or biodegradable materials has attracted both academic and industrial interests [19][20][21].…”