**3. Room temperature ionic liquids**

Ionic liquids or room temperature ionic liquids (RTILs) are defined as molten salts (composed entirely of cations and anions) that melt below 100°C [33] with remarkable physicochemical properties: non-flammable, non-corrosive, nonvolatile, and bulk physical constant, which can be tuned by the combination of different cations and anions [34–38]. RTILs are composed by bulky organic cations usually imidazolium or pyridinium derivatives substituted with alkyl chains and an inorganic or organic anion (usually a halide, tetrafluoroborate, hexafluorophosphate, and others). The high combinatorial flexibility has converted these materials into "designer solvents" or "task-specific" solvents [33, 35, 38] whose properties can be specified to suit the requirements of a particular reaction [2, 4, 12, 39]. For these reasons, RTILs have gained importance in the solvent effects field being recognized as very promising reaction media with green features.
