L-alkyl-3-methylimidazolium salts

In general, isotopic exchange is both expensive and difficult. In tlie case of many room-temperature ionic liquids, however, the manufacture of deuterated ionic Hq-uids is relatively easily achievable. For example, the general synthesis of l-alkyl-3-methylimidazolium salts is shown in Scheme 4.1-1 [2]. This methodology allows maximum flexibility in the deuteration on the imidazolium cation that is, it can be either ring or side chain deuteration or both. 

Bradley, A. E., Hardacre, C., Holbrey, J. D., Johnston, S., McMath, S. E. J., and Nieuwenhuyzen, M., Small-angle x-ray scattering studies of liquid crystalline l-alkyl-3-methylimidazolium salts, Chem. Mater., 14,629-635,2002. 

Lin, S.-T., Ding, M.-R, Ghang, C.-W. et al.. Nuclear magnetic resonance spectroscopic study on ionic liquids of l-alkyl-3-methylimidazolium salts. Tetrahedron, 60, 9441,2004. 

Separation of C02 from N2 or CH4 comprises an area of critical industrial, social, and environmental importance where room-temperature ionic liquids (RTILs) are showing great potential [3, 63, 64], The commonly used ILs for this purpose are l-alkyl-3-methylimidazolium salts, represented by the formula [C MIm][X, where C is an n-alkyl chain of varying length and X is typically a molecular anion with a delocalized negative charge, such as bis(trifluorome-thane)sulfonimide, [Tf2N ] (Scheme 4.4) [65-71]. 

Ethylammonium nitrate (entry 18 in Table 3-1) was shown in 1914 to have m.p. 12 °C and was hence the first room temperature ionic Hquid [156] this was followed in 1967 by tetra- -hexylammonium benzoate with m.p. —50 °C (entry 26) [169], Ambient-temperature ionic liquids based on l-alkyl-3-methylimidazolium salts (entries 19-24) were first reported by Wilkes et al. in 1982 as tetrachloroaluminates [162a], Replacement of this moisture-sensitive anion by the tetrafluoroborate ion and other anions led, in 1992, to air- and water-stable, room temperature ionic liquids [162b], which have since found increasing application as reaction media for various kinds of organic reactions, mainly owing to the work of Seddon [167, 190] and Hussey [187], Suitably selected... 

The fluorescent probe 4-aminophthalimide (63) as well as its /V,/V-diethyl homomorph (89) were used by Samanta and coworkers148 149 to study the polarity and fluorescence dynamics in l-alkyl-3-methylimidazolium salts. The alkyl groups were variously ethyl, butyl and octyl and the anions were nitrate, tetrafluoroborate, hexafluorophosphate and bis(triflyl)imide. Similar conclusions were reached concerning the effects of alkyl chain length and anion as those obtained by Carmichael and Seddon142 using Nile Red. The solvation dynamics were found to depend on the viscosity of the media. Further use of 63 in l-butyl-3-methylimidazolium hexafluorophosphate was reported by Ingram and... 

Aupoix A, Pdgot B, Vo-Thanh G (2010) Synthesis of imidazolium and pyridinium-based ionic liquids and application of l-alkyl-3-methylimidazolium salts as pie-catalysts for the benzoin condensation using solvent-free and microwave activation. Tetrahedron 66 1352-1356... 

In contrast to sodium, a residual Lewis base such as the starting N-alkylimidazole can severely poison organometallic catalysts. These compounds are coordinating bases and have been proven difficult to remove from ILs due to their high boiling points. A simple colorimetric method of detection was first developed, which is based on the complexation of N-methylimidazole with copper(II) chloride [13]. ft enables monitoring of N-methyhmidazole content in [EM1][C1] to better than 0.2 mol%. More recently, capillary electrophoresis was applied for the detection of imidazole derivatives in l-alkyl-3-methylimidazolium salts [14]. Using this technique, it is then possible to separate and identify the different N-alkylimidazole and imidazolium cations in the ILs. 

Catecholamines. The use of l-alkyl-3-methylimidazolium salts and N-butyl-pyridinium salts as mobile phase additives for the separation of catecholamines in reversed phase HPLC has been reported (14). As catecholamines, norepinephrine, epinephrine and dopamine were investigated. These compounds are shown in Figure 1.8. 

Bradley AE, Hardacre C, Holbrey ID, Johnston S, McMath SEJ, Nieuwenhuyzen M (2002) SmaU-angle X-ray scattering studies of Uquid crystalline l-alkyl-3-methylimidazolium salts. Chem Mater 14(2) 629-635. doi 10.1021/cm010542v... 

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