Ionic Liquid Preparation

When [EMIMJCl is present in a molar excess over AICI3, only equilibrium (2.1-1) need be considered, and the ionic liquid is basic. When a molar excess of AICI3 over [EMIMJCl is present on the other hand, an acidic ionic liquid is formed, and equilibria (2.1-2) and (2.1-3) predominate, further details of the anion species present may be found elsewhere [23]. The chloroaluminates are not the only ionic liquids prepared in this manner. Other Eewis acids employed have included AlEtCl2 [24], BCI3 [25], CuCl [26], and SnCl2 [27]. In general, the preparative methods employed for all of these salts are similar to those indicated for AlCl3-based ionic liquids as outlined below. 

Table 2.1-1 Examples of ionic liquids prepared by anion metathesis.

Ionic liquid synthesis in a commercial context is in many respects quite different from academic ionic liquid preparation. While, in the commercial scenario, labor-intensive steps add significantly to the price of the product (which, next to quality, is another important criterion for the customer), they can easily be justified in academia to obtain a purer material. In a commercial environment, the desire for absolute quality of the product and the need for a reasonable price have to be reconciled. This is not new, of course. If one looks into the very similar business of phase-transfer catalysts or other ionic modifiers (such as commercially available ammonium salts), one rarely finds absolutely pure materials. Sometimes the active ionic compound is only present in about 85 % purity. However, and this is a crucial point, the product is well specified, the nature of the impurities is known, and the quality of the material is absolutely reproducible from batch to batch. 

Ionic liquids prepared as low-melting salts. .. [NR3R ]Cl/ZnCl2 University of Leicester, UK 2000 29... 

For the results reported in both Table 7.2-3 and Table 7.2-4, the only reported detail concerning the ionic liquid was that it was [EMIM][C1-A1C13]. No details of the aluminium(III) chloride content were forthcoming. As with most of the work presented in this chapter, data are taken from the patent literature and not from peer reviewed journals, and so many experimental details are not available. This lack of clear reporting complicates issues for the synthetic polymer chemist. Simpler and cheaper chloroaluminate(III) ionic liquids prepared by using cations derived from the reaction between a simple amine and hydrochloric acid (e.g., Me3N-E3Cl and... 

Cao, S.W. and Zhu, Y.J. (2009) Iron oxide hollow spheres microwave-hydrothermal ionic liquid preparation, formation mechanism, crystal phase and morphology control and properties. Acta Materialia, 57 (7), 2154-2165. 

Dyson recently warned that chloride impurities present in ionic liquids prepared by the classical metathesis reaction may cause severe catalyst inhibition. This may be aggravated by the fact that metal-chloride dissociation is disfavored in ionic liquids, in spite of their polar nature [77]. 

The new ILs, submitted to differential scanning calorimetry analysis, showed glass-transition temperatures ranging from —36°C (47c) to +18°C (47a). All the ionic liquids prepared were stable compounds that did not undergo hydrolysis of the anomeric C-N bond upon prolonged storage at room temperature. Moreover, their... 

Campbell, J. L. E., Johnson, K. E., and Torkelson, J. R., Infrared and variable-temperature H-NMR investigations of ambient-temperature ionic liquids prepared by reaction of HCl with l-ethyl-3-methyl-lH-imidazolium chloride, Inorg. Chem., 33, 3340,1994. 

Protocol for the Deposition of Zinc from a Type III Ionic Liquid Preparation of Ionic Liquids... 

When the temperature is changed, the Nyquist plot also changes, as shown in Figure 6.4 , due to the change in conductivity. Figure 6.4 shows the Nyquist plots for the ionic liquid prepared by the neutralization of l-benzyl-2-methylimidazole and HTFSI. The temperature dependence of the ionic conductivity is generally depicted by an Arrhenius plot (Figure 6Ab). 

TABLE 12.1 Lowest Temperature (°C) to Solubilize 1 wt% DNA Into Ionic Liquids Prepared by the Neutralization of Corresponding Bases and Acids... 

It is important to select for salts suitable ion species with excellent properties. However, the ions must be counter ions that are oppositely charged in ordinary conditions, which makes it impossible to couple a suitable cation and anion. Therefore the salt mix must contain the suitable cation and anion. Then the target salts are isolated from the mixture. Because the solubility (or miscibility) of different salts in molten salts must be taken into account, it is usually difficult to isolate the target salts. Of course, there are some salts that can easily be separated. For example, hydrophobic salts such as some l w(trifluoromethanesulfonyl)imide (TFSI) salts can be separated from hydrophilic salts by washing the salt with water. Some other systems are known to separate with fairly good yield. It should be noted here that there is no systematic method to use in preparing any kind of salts from a mixture. This is stiU a serious problem of ionic liquid preparation, especially for the scientists who wish to create (or find) new ionic liquids. 

It is well known that amines can be neutralized with acids to generate salts. This neutralization process is useful in preparing organic salts with very low melting points. In 1914 Walden reported [3] neutralized ethylamine with nitric acid to prepare a salt that had a melting point of 12°C. This appears to have been the first ionic liquid prepared by a neutralization method [4]. As seen in equation (19.1), there is a slight difference between onium cations prepared by quaternization (a) and neutralization (b) when tertiary amines are used as a starting material ... 

Ohno H, Yoshizawa M. Ion conductive characteristics of ionic liquids prepared by neutrahzation of alkylimidazoles. Solid State Ionics. 2002. 154-155, 303-309. 

Leclercq L, Suisse I, Nowogrocki G et al (2007) Hahde-free highly-puie imidazohum triflate ionic liquids preparation and use in palladium-catalysed aUyUc alkylation. Green Chem 9 1097-1103... 

Table 8.10 Examples of ionic liquids prepared from reactions of [XjCl and a Lewis acid where [X] is an alkylpyridinium or dialkylimidazolium ion.

Ohno, H., and M. Yoshizawa. 2002. Ion Conductive Characteristics of Ionic Liquids Prepared by Neutralization of Alkylimidazoles. Solid State Ionics 154-155 303-309. 

Deetlefs, M. and Seddon, K.R., Assessing the greenness of some typical laboratory ionic liquid preparations. Green Chem. 12, 17-30 (2010). 

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