Current Green Chemistry   Send Orders for Reprints to reprints@benthamscience.net Current Green Chemistry, 2020, 7, 105-119 105 MINI REVIEW ARTICLE Task-specific Ionic Liquids as a Green Catalysts and Solvents for Organic Synthesis Swapnil A. Padvi 1 and Dipak S. Dalal 2,* 1 Department of Chemistry, Jai Hind Educational Trust Z. B. Patil College, Dhule – 424 002 (M. S.), India; 2 School of Chemical Sciences, Kavayitri Bahinabai Chaudhari North Maharashtra University, Jalgaon - 425 001 (M. S.), India Abstract: Task-specific ionic liquids (TSILs) have received increased attention over the past few years as a Green Catalysts and Solvents for a large number of organic transformations. The present re- view article aims to provide an introduction, types of task-specific ionic liquids, preparation/synthesis, physical properties, characterization, use of TSILs as solvent and catalyst in organic synthesis. A R T I C L E H I S T O R Y Received: June 29, 2019 Revised: December 11, 2019 Accepted: December 13, 2019 DOI: 10.2174/2213346107666200115153051 Keywords: Task-specific ionic liquids, green chemistry, organic synthesis, Ionic liquids (ILs), molten salts, typical cations. 1. INTRODUCTION To date, molecular solvents were used for most of the chemical processes [1, 2]. These molecular solvents can in- duce environmental pollution due to the use of huge amounts in the chemical industry and laboratory may cause environ- mental problems and creates adverse effects on organisms and human health because they are toxic, flammable, explo- sive and volatile [3, 4]. Among the several important princi- ples of green chemistry, the elimination of hazardous sol- vents and catalyst has attracted significant attention world- wide to avoid the generation of chemical wastes [5]. Re- searchers both from academia and the industry have been focused on reducing or eliminating the use of toxic solvents to minimize damage to the environment [6] and search for a safer solvent and catalyst alternative is thus holding a key role in the green chemistry. Ionic liquids have been recognized as a new green chem- ical revolution which excited both the scientific community from the academia and the chemical industries. This peculiar class of molecular solvent can reduce the use of hazardous and polluting organic solvents due to their useful properties [7]. Ionic liquids are known as salts that are liquid consist- ing of ions (organic cations and anions), but it is different from molten salts [8-10]. Molten salts are usually defined as a high melting, highly viscous and highly corrosive liq- uid, while ionic liquids are defined as pure compounds, *Address correspondence to this author at the School of Chemical Sciences, Kavayitri Bahinabai Chaudhari North Maharashtra University, Jalgaon - 425 001 (M. S.), India; Tel: +91-2572257432; Fax: +91-257-2258403; E-mail: dsdalal2007@gmail.com entirely composed of ions which melt at or below 100°C (212°F) [11]. Ionic liquids (ILs) have attracted great considerable at- tention in the context of green chemistry. They have eco- friendly alternatives to conventional and environmentally detrimental molecular solvents for many chemical applica- tions in the field of sciences due to their unique chemical and physical properties [12-15] that are principally in accordance to a green chemistry point of view, such properties include chemical stability, thermal stability, non-flammability, non- volatility, precise miscibility, and recyclability. 2. HISTORY The first ionic liquid reported was ethyl ammonium ni- trate [EtNH 3 ][NO 3 ] (m.p. 12°C) in 1914 by Paul Walden [16]. In between the 1970s and 1980s, ionic liquids based on alkyl-imidazolium and pyridinium cations, with halide or tetra halogenoaluminate anions, were developed as potential electrolytes in batteries [17]. Afterwards, the first generation of ILs appeared and was widely described by Wilkes and co- workers in 1982 as a Room-temperature ILs (RTILs) based on typical cations i.e. 1-alkyl-3-methylimidazolium and tetrachloroaluminates as an anion [18]. This salt is liquid at room temperature and possesses favorable physical and elec- trochemical properties but sensitive to moisture, usually con- tains a small amount of water. The second generation of ILs invented as an air and moisture stable ILs by replacing the tetrafluoroborate ion and other anions instead of the mois- ture-sensitive anion led in 1992 [19]. These ILs have suc- cessfully been used as a reaction media for various kinds of organic reactions. The third generation of ILs introduced by Davis and co-workers in 2004 as a task-specific ionic liquids (TSILs) to describe ILs in which a functional group is cova- 2213-347X/20 $65.00+.00 © 2020 Bentham Science Publishers