The study of extent of interactions between components of natural deep eutectic solvents in the presence of water through isopiestic investigations

In this work, from the vapor-liquid equilibrium (VLE) studies on the two synthesized natural deep eutectic solvents (NADESs) containing choline chloride divided by sucrose with molar ratio 1:1 or fructose with molar ratio 2:1 and corresponding mixtures with the same molar ratios with addition of different amount of water, the effect of dilution on the existing hydrogen bonding interactions in these DESs was investigated at 298.15 K. The measured water activity and isopiestic equilibrium water mass fraction values were used to investigate the extent of these hydrogen bonding interactions by dilution. These results suggest that the H-bonding interaction between two components of both NADESs are weakened by addition of water to each NADES and when the water content is exceeded 75% (g/g) the H-bonding is mostly disappeared. In addition, to investigate a possible interactions between choline chloride and sucrose or fructose, the isopiestic measurement were also carried out on the aqueous systems containing {choline chloride + sucrose) and {choline chloride + fructose) at 298.15 K. The obtained water activity lines showed that both of these systems have positive deviation from the semi-ideal solution and therefore choline chloride has favorable interactions with fructose or sucrose. In order to find further evidence for these favorable interactions, volumetric and acoustic studies were also made on these ternary solutions by measuring density and speed of sound values. From these data, the limiting values for the apparent molar volume (V-phi(0)), apparent molar isentropic compressibility (k(phi)(0)) and the standard transfer volumes (Delta V-t(phi)0) were obtained which again indicate favorable interactions between choline chloride and sucrose or fructose. (C) 2020 Elsevier B.V. All rights reserved.