Choline chloride based brønsted and lewis acid ionic liquids as catalysts for organic reactions

Abstract

Organic synthesis is an ever increasing and ever demanding area in the fields of bulk and fine chemical pharmaceutical and biological industries A vast variety of inorganic catalysts possessing wide range of physicochemical characteristics were employed to enhance the efficiency of organic reactions Many of the industrially significant synthetic processes proceed via application of metallic metal oxide and metal salt based heterogeneous catalytic systems The disposal of industrial waste also carries a high demand with respect to ecological point of view In this scenario Ionic liquids serve as eco friendly and biocompatible alternatives to many volatile organic solvents that are employed in industries Ionic liquids are such solvents that possess inherent solvent characteristics tunable acidity as well as basicity thermal and chemical stability wide liquid range and biodegradability Ionic liquids find extensive applications in fields such as electrochemical metal deposition pharmaceuticals and photocatalysis They serve not only as successful solvents but also as excellent catalytic systems and paved the route for solvent free mediated organic syntheses Even though a versatile class of ionic liquids were discovered for organic reactions some ionic liquids such as chloroaluminate and imidazolium suffer from disadvantages such as toxicity instability and moisture sensitivity In this context choline chloride ChCl based ionic liquids are viewed as eco friendly and greener alternatives Choline chloride is regarded as member of vitamin B family and serves as an important growth accelerator to improve the feed efficiency in poultry In combination with different compounds it forms various types of ionic liquids with tunable acidity newline