Insights into the Hydrogen Bond Interactions in Deep Eutectic Solvents Composed of Choline Chloride and Polyols

Deep eutectic solvents (DESs) consisting of cholinium chloride (ChCl) and alcohols have been widely applied in the purification of bioactive compounds, biodiesel and flavonoids. However, an explicit and complete knowledge of the interactions between ChCl and alcohols are still lacking. In this work, the interactions between ChCl and polyols (1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,3-propanediol, glycerol, 1,5-pentanediol, 1,2,5-pentanetriol and xylitol) have been investigated at different molar ratios of ChCl to polyols by Fourier transform middle infrared, far infrared, 1H and 35Cl NMR spectroscopy as well as quantum chemistry calculation. It is shown that hydrogen bond interaction between Cl atom of ChCl and H atom of O-H group in the polyols is predominant and its strength decreases with both the increase of carbon number between two hydroxyl groups in butanediol and the decrease of hydroxyl number in polyols. As butanediol content is increased in the mixture, the hydrogen bon...