With many chemical transformations taking place in solution, the role of solvents in chemistry is vital. Although, in principle, any liquid could be employed as a solvent, polar organic solvents have extensively been used for both synthetic chemistry and extraction technologies and have largely superseded water, which was widely employed historically. However, the ever-increasing awareness of the detrimental health and environmental effects of some organic solvents has given chemists the impetus to search for ‘green’ technologies.

The obviously ideal situation for a chemical process, from an ecological point of view, involves no solvent. Although many reactions can be performed without solvent, chemistry remains dominated by processes taking place in solution. Nowadays, there are several alternatives under investigation as solvents including the resurgence of water, perfluorinated hydrocarbons, molten salts (ionic liquids) and supercritical fluids, in particular CO2. The use of these media as solvents for the generation of ‘green’ technologies will be discussed and in particular the main achievements on the use of room temperature ionic liquids in the area of green chemistry disclosed in the last two years.