Eutectic System Based on Urea and Potassium Sodium Tartrate

Deep eutectic solvents (DESs) are considered as better alternative solvents in chemical and physical processes. The binary mixture of urea and potassium sodium tartrate is explored in this study. A eutectic system is determined at composition made up of 33% potassium sodium tartrate and 67% urea (1:2 molar ratio). This eutectic system has a freezing point of 19.83 ± 0.76 °C, density of 1.1971 ± 0.0003 g mL-1, and viscosity of 34.4226 ± 0.0665 cP. The most stable conformation for the adduct of urea and potassium sodium tartrate with water molecules was determined through density functional calculations. The gas phase total energy for the adduct was determined as -5576863 kJ mol-1. Electrostatic interactions between the cations and the carboxylate sites are present, H-bonding between protons of urea and the hydroxyl oxygen of the tartrate, and intramolecular H-bonding between the hydroxyl and carboxylate sites of tartrate are accounted in the structure. The total energy associated with nonbonding interactions is computed as -826 kJ mol-1, which suggests that these interactions stabilize the formation of the DES system of potassium sodium tartrate and urea.