NMR study of choline chloride-based deep eutectic solvents

Abstract

Nowadays, the eutectic liquids (DESs) are considered an adequate alternative to the traditional solvents. Therefore, there is an increasing interest in the study of the structure, properties and applications of these mixtures. In this paper, several NMR spectroscopic techniques have been used in order to evaluate the molecular structure of three ternary DESs, composed of choline chloride, urea or glycerol or ethylene glycol, and water. The use of routine and non-routine NMR techniques, such as 1H, 13C, correlation experiments, NOESY, ROESY, and diffusion experiments gave us some important evidences pointing to a supramolecular structure of the DES, which may be the origin of their particular behaviour. The mixture containing ethylene glycol shows the feeblest structure. In these ternary solvents, the water is found within the structure that is still retained when DESs are diluted at 10% wt.