The standard entropies S298°E of deep eutectic solvents (DESs), which are liquid binary mixtures of a hydrogen bond acceptor component and a hydrogen bod donor one, are calculated from their molecular volumes, derived from their densities or crystal structures. These values are compared with those of the components-pro-rated according to the DES composition-to obtain the standard entropies of DES formation ΔfS. These quantities are positive, due to the increased number and kinds of hydrogen bonds present in the DESs relative to those in the components. The ΔfS values are also compared with the freezing point depressions of the DESs ΔfusT/K, but no general conclusions on their mutual relationship could be drawn.
Keywords: deep eutectic solvent (DES); hydrogen bonding; molecular volume; standard entropy.