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Choline chloride (ChCl) has been combined with renewable hydrogen bond donors (HBD) to form novel deep eutectic solvents (DES) with melting points lower than 100 °C. In some cases (e.g. sorbitol or isosorbide as HBDs) chiral DES can be easily produced. Moreover, the addition of glycerol decreases the viscosity of DES significantly. In the ChCl : levulinic acid DES case, singular properties were observed. Thus, equimolecular mixtures of ChCl : levulinic acid (1 : 1) formed a crystal at room temperature, rapidly melting in contact with air humidity. Addition of excess of acetone to ChCl : levulinic acid (1 : 2) leads to the almost quantitative precipitation of choline chloride, which can be used again to form a DES.
Maugeri et al. (Fri,) studied this question.