Title : Deep eutectic solvents in chemistry: Novel frontiers
Abstract:
Over the years, there has been a growing demand of green and ecologically relevant chemical media. The incentive of incorporating green approach is derived from the urge to combat the burgeoning environmental issues that have existed so far. In the recent years, deep eutectic solvents (DESs) with properties somewhat analogous to ionic liquids (ILs) nonetheless with additional advantages are developing as a neoteric category of solvents owing to their favorable features and properties associated with them. DESs are liquids having low melting points formed by the combination of salts such as choline chloride with urea or other hydrogen-bond donating (HBD) components. Prepared by simple mixing of two or more compounds at a definite mole ratio and gentle heating, the resulting DES is a liquid phase stable at a temperature much lower than the individual melting temperatures of the constituents. DESs are documented to be environmentally-benign, have good thermal stability, high conductivity, negligible vapor pressure, wide electrochemical window, non-flammability, composed of cheap and non-toxic materials and are capable of dissolving a plethora of solutes. The hydrogen bonding network which is responsible for the remarkable depression in the melting point of DESs is revealed to be far more complicated that any one of the existing propositions/hypotheses put forward till now. The copious amount of research endeavors focused on these novel solvents have unearthed their promising behavior in solving related engineering problems. DES-based systems with modified physicochemical properties hold scope for breaking new ground in futuristic applications of synthesis, polymerization, electrochemistry, material sciences, and many other fields. With the research on DESs still in its infancy, the future bears noteworthy potential to expand the range of salts and HBDs which can be exploited to further widen the horizon of these green solvents.
