Ionic liquids physicochemical properties

Effect of Anion on Ionic Liquid Physicochemical Properties... 

Greaves, T.L., Weerawardena, A., Krodkiewska, I. and Drummond, C.J., Protonic ionic liquids Physicochemical properties and behavior as anphiphile self-assembly solvents, J. Phys. Chem. B 112 (3), 896-905 (2008). 

Greaves TL, Weerawardena A, Krodkiewska I, Drummond CJ (2008) Protic ionic liquids physicochemical properties and behavior as amphiphile self-assembly solvents. J Phys Chem B 112 896-905... 

This section attempts to show how ionic liquids are able to modify the kinetic and stereochemical course of organic reactions. It will cover, therefore, only a limited number of reactions and even a more limited number of ionic liquids, mainly those reported in Table 5.IT. Unfortunately, only a few ionic liquids have been used in studies of reactivity and for even fewer are aU of the physicochemical properties required to rationalize organic reactivity known. Sometimes, the data reported in the literature have been revised and reinterpreted in the light of more recent findings on the physicochemical properties of the applied ionic liquids. I express regret if I have misunderstood some results or some interpretations. My aim is merely to promote the discussion about ionic liquids solvent properties in order to increase the understanding of these neoteric solvents and favor the development of more efficient processes. 

Water in an ionic liquid may be a problem for some applications, but not for others. However, one should in all cases know the approximate amount of water present in the ionic liquid used. Moreover, one should be aware of the fact that water in the ionic liquid may not be inert and, furthermore, that the presence of water can have significant influence on the physicochemical properties of the ionic liquid, on its stability (some wet ionic liquids may undergo hydrolysis with formation of protic impurities), and on the reactivity of catalysts dissolved in the ionic liquid. 

From all this, it becomes understandable why the use of traditional solvents (such as water or butanediol) for biphasic catalysis has only been able to fulfil this potential in a few specific examples [23], whereas this type of highly specialized liquid-liquid biphasic operation is an ideal field for the application of ionic liquids, mainly due to their exactly tunable physicochemical properties (see Chapter 3 for more details). 

Table 4.1 Names, Structures, and Physicochemical Properties of Selected Ionic Liquids Evaluated as Gas-Liquid Chromatographic...

Tokuda, H., Hayamizu, K., Ishii, K. et al.. Physicochemical properties and structures of room temperature ionic liquids. 1. variation of anionic species, /. Phys. Chem. B, 108,16593,2004. 

GAP is synthesized by replacing C-Cl bonds of polyepichlorohydrin with C-N3 bonds.The three nitrogen atoms of the N3 moiety are attached linearly with ionic and covalent bonds in every GAP monomer unit, as shown in Fig. 4.6. The bond energy of N3 is reported to be 378 kj moh per azide group. Since GAP is a liquid at room temperature, it is polymerized by allowing the terminal -OH groups to react with hexamethylene diisocyanate (HMDI) so as to formulate GAP copolymer, as shown in Fig. 4.7, and crosslinked with trimethylolpropane (TMP) as shown in Fig. 4.8. The physicochemical properties of GAP prepolymer and GAP copolymer are shown in Table 4.4 and Table 4.5, respectively. ]... 

The temperature range within which ionic liquids occur in the liquid state is very characteristic it is assumed that it is never greater than 300°C. No other type of commonly used solvent occurs as a liquid over such a great range. Table 19.7 lists the physicochemical properties of frequently used solvents. 

Table 2.2 Dependence of selected physicochemical properties (at 20°C) of ionic liquids [EMIMJXon the anion X-.

The choice of anion will have a known effect on the physicochemical properties of the ionic liquid. To demonstrate the anion effect, selected data on properties of general interest to electrochemists (density, viscosity, conductivity and electrochemical window) have been gathered in Table 2.2. In each case, the anion is paired with the same cation l-ethyl-3-methylimidazolium. Certain trends from this data can be generalized, as well as in other collections of such data (for example, see Ref. [61] and references therein), that hold true regardless of the identity of the cation. For example, the effect of the anion on density follows the trend ... 

In this chapter we report on the electrodeposition of semiconductors in ionic liquids. It is shown that ionic liquids are, due to their extraordinary physicochemical properties, well suited as a solvent medium for the electrodeposition of elemental semiconductors (like Si and Ge), their mixtures (Si Gei %) and compound semiconductors (GaAs, AlSb, InSb, ZnTe, CdTe, CuInSe2, etc.). 

Like other salt melts ionic liquids are characterized by a specific combination of physicochemical properties high ionic conductivity, low viscosity, high thermal stability compared to conventional liquid solvents, wide electrochemical windows of up to 7 V and - in most cases - extremely low vapor pressures. Due to their low vapor pressure ionic liquids are not only well suited for the application of UHV-based analytical techniques (e.g. photoelectron spectroscopy [3]), but also for use in plasma reactors with typical pressures of the order of 1 Pa up to 10 kPa. Moreover, due to their high electrical conductivity, ionic liquids may even be used as electrodes for plasmas. To date there are just a few reports on the combination of low-temperature plasmas and ionic liquids available in the literature [4—6]. Therefore, the essential aspects of experiments with ionic liquids in typical plasma reactors are discussed in this section. 

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