Investigation of deep eutectic solvents based on polyatomic alcohol, quaternary ammonium salt and carbonic acid diamide by IR spectroscopy
A. R. SAIDENTSAL, M. R. SHOLIDODOV
Institute of Petroleum Chemistry, Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
Keywords: deep eutectic solvents, donor-acceptor interaction, eutectic, IR spectroscopy, phase diagram, two-component system, three-component system
Abstract
Two- and three-component systems of deep eutectic solvents (DES) based on polyatomic alcohol - pentaerythritol (PER), carbonic acid diamide - urea (carbamide, CA) and quaternary ammonium salt - choline chloride (CC) were synthesised: PER-CC, PER-CA, CC-CA, PER-CA-CC. Eutectic points in the obtained DES systems were determined. It is shown that the lowest melting point (-14.5 °C) is observed for the three-component DES system based on PER-CA-CC with the molar component ratio of 1.3 : 2.4 : 1, respectively. The solubility of this three-component system was determined by dissolution in water prior to precipitation. The density of the aqueous solutions of binary DES systems was determined to be within the range of 1.2158-1.2458 g/cm3. The presence of hydrogen bonds in binary and ternary DES systems was revealed by IR spectroscopy: CC acts as an acceptor of hydrogen bonds, while PER and CA act as donors. The presence of hydrogen bonds between DES components provides the formation of stable molecular complexes and lowering of the melting/crystallisation points of DES compositions due to intermolecular bond weakening and destruction of the crystal structures of initial substances.
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