Ionic liquids: Green solvents of sustainable chemistry

Abstract

Sustainable chemistry is determined for the reduction or replacement of chemicals which causes irreparable damage to ecosystem and raises environment, health and safety concerns. Conventional organic solvents are main culprit in increasing the non-greenness of chemical processes by emitting out volatile organic carbons into the atmosphere. Novel and green solvents such as ionic liquids (ILs) are proved as stepping stone for the design of more eco-viable chemical processes. ILs are ‘liquid’ ‘salts’ which consists of large hydrophobic cationic part and smaller inorganic anionic part. They have a unique array of physic-chemical properties which make them suitable in numerous applications in which conventional organic solvents are not sufficiently effective or not applicable. Main factor which contribute in green nature of ILs is their non-volatile nature which is due to electrostatic forces of attraction between cationic and anionic part. This force is strong enough to negate their vapor pressure by holding the cations and anions in ILs and weak enough to make them to exist in liquid state. ILs have been successfully used as substitutes of conventional solvents & catalysts in organic synthesis, extraction of variety of chemicals and metal ions, dissolution of lignocellulosic material, nanoparticle synthesis etc. In this present review article, various aspects of ILs including their application in various fields are addressed.