During last years the interest in so called "green chemistry", i.e. environment friendly chemistry has grown causing start of researches on new solvents which do not emit any vapours. These researches has resulted in the IONIC LIQUIDS discovery. Those liquids meet all requirements related to the "green" solvents.

    The IONIC LIQUIDS are organic salts, which keep their liquid state at low temperatures (< 100 °C), representing the new class of solvents of ionic characteristics¹. They are salts consisting of an organic cation and an anion as well of organic as inorganic characteristics. The most popular ionic liquids contain the following cations: imidazolium, piridinium, ammonium and phosphonium. The range of anions used is also wide, popular ones are: tetrafluoroborate, hexafluorophosphate, nitrate, di(trifluorosulfonil)amide or trifluoroacetate.

    The IONIC LIQUIDS characteristic feature is that their physical and chemical properties can change in a wide range depending on cation and anion chemical structure. Potentially there is the possibility to select ions in such a way to obtain a ionic liquid of specific, desired properties (viscosity, density, miscibility with water and organic solvents). That is the reason why IONIC LIQUIDS are often called as DESIGNER SOLVENTS.

    The IONIC LIQUIDS present many properties which cause that they can become an attractive reaction media:

• they are not volatile, vapour pressures of ionic liquids have non-measurable values. They cannot be distilled (boiling point is decomposition temperature) while a product can be distilled off. Also the well known problem of an azeotrope creation between product and solvent¹ does not exist in this case,
• they show high thermal stability, many ionic liquids keep their liquid state in a wide, above 300 °C, temperature range²,
• they are good solvents for a wide range of organic, inorganic and organometallic compounds,
• they are immiscible with many organic solvents e.g. alkanes, what allows their use in diphase systems,
• lipophil ionic liquids due to their immiscibility with water can be used in liquid-liquid extraction.

    Researches carried on all over the world confirmed that IONIC LIQUIDS can be used as reaction media for many syntheses: hydrogenation, Friedl-Crafts reaction, Diels-Alder reaction, polymerization, alkylation, allylation, Heck reaction, hydroformylation, enzyme-catalyzed reactions.

    More information about IONIC LIQUIDS can be found in:

1. Wasserscheid, P., Keim, W. Angew. Chem. Int. Ed., 2000, 39, 3772-89
2. Sheldon, R. Chem. Commun., 2001, 2399-2407
3. Welton, T. Chem. Rev. 1999, 99, 2071-2084
4. Dupont, J., de Souza, R.F., Suarez, P.A.Z. Chem. Rev. 2002, 102, 3667-3692
5. Zhao, H., Malhotra, S.V. Aldrichimica Acta 2002, 35(3), 75-83
6. Rogers, R.D., Seddon, K.R. Egs. Ionic Liquids: Industrial Application for Green Chemistry, Oxford University Press, New York, 2002
7. Wasserscheid, P., Welton, T. Ionic Liquids in Synthesis, John Willey & Sons, New York 2002
8. Baudequin,C., Baudoux, J., Levillain, J., Cahard, D., Gaumont, A.C., Plaquevent, J.C. Tetrahedron Asymmetry 2003 14, 3081-3093
9. Pernak,J. Przem Chem. 2003, 82, 521-524

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