Ionic liquids solvent properties

For a recent review on ionic liquid solvent properties see C. Chiappe, D. Pieraccini, J. Phys. Org. Chem. 2005,18, 275. 

Chiappe C, Pieraccini D (2005) Ionic liquids solvent properties and organic reactivity. J Phys Org Chem 18 275-297... 

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. 

Chiappe, C., Pieraccini, D. (2005). Ionic liquids Solvent properties and organic reactivity. 

The possibility of adjusting acidity/coordination properties opens up a wide range of possible interactions between the ionic liquid solvent and the dissolved transition metal complex. Depending on the acidity/coordination properties of the anion and on the reactivity of the cation (the possibility of carbene ligand formation from 1,3-dialkylimidazolium salts is of particular importance here [37]), the ionic liquid can be regarded as an innocent solvent, as a ligand precursor, as a co-catalyst or as the catalyst itself. 

Greaves T L, Weerawardena A, Fong C, et al. Protic ionic liquids Solvents with tunable phase behavior and physicochemical properties. 

Wilkes JS. 2004. Properties of ionic liquid solvents for catalysis. J Mol Catal A Chem... 

As mentioned above, ionic liquids are now available from a number of commercial manufacturers and from many suppliers. Still, one should not forget that an ionic liquid is a quite different product compared to traditional organic solvents, simply because it caimot be easily purified by distillation, due to its very low volatility. This, combined with the fact that small amounts of impurities influence the ionic liquid s properties significantly [9] makes the quality of an ionic liquid a quite important consideration for many applications. 

The dynamic behavior of ionic liquids is important for both practical and theoretical reasons. From a practical standpoint, bulk transport properties such as the viscosity, self-diffUsivity, thermal conductivity and electrical conductivity govern the effectiveness of these liquids in any application. For example, mass transfer of reactants and products is critical to the performance of ionic liquid solvents, and is highly correlated with the self-difiiisivity and viscosity. Viscosity also plays a role in the cost of pumping the liquid and its performance as a lubricant. Thermal conductivity is a key parameter for thermal fluid applications, and electrical conductivity is obviously important in electrochemical applications. 

Goujon, N., Wang, X., Rajkowa, R., Byrne, N., 2012. Regenerated silk fibroin using protic ionic liquids solvents towards an all-ionic-liquid process for producing silk with tunable properties. Chentical Communications (Cambridge, England) 48 (9), 1278-1280. 

Wilkes, J. S. 2004. Properties of Ionic Liquid Solvents for Catalysis. Journal of Molecular Catalysis A Chemical 214 (1) 11-17. 

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). 

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