Abstract

Ethyl ((1R,2S,5R)-2-isopropyl-5-methylcyclohexane-1-carbonyl) glycinate (Cooling agent WS-5) is an important cooling menthane carboxamide. In this work, the solid–liquid equilibrium data of WS-5 in twelve mono solvents (namely methanol, ethanol, n-propanol, isopropanol, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, acetone, acetonitrile and cyclohexanone) were measured by a laser dynamic method from 278.15 K to 313.15 K under 101.6 ± 1.2 kPa. In the studied temperature range, the solubility of WS-5 correlated positively with temperature. Subsequently, the solubility data were correlated with the van't Hoff equation, modified Apelblat equation, λh equation, Wilson model, and NRTL model, respectively. It was found that the modified Apelblat equation showed the best fitting performance with the smallest average values of RAD (relative average deviation) and RMSD (root mean square deviation), and the average values of RAD and RMSD were 0.94 % and 0.19 %, respectively. In order to explain the dissolution behavior of WS-5 in different solvents, the intermolecular interactions were analyzed using Hirshfeld surface (HS) analysis and molecular electrostatic potential surface (MEPS). Then, the molecular dynamic (MD) calculation was carried out, and the radial distribution function (RDF) analysis was employed to explain the intermolecular interaction between WS-5 and solvent molecules. Besides, the solvent properties, including polarity, hydrogen bond, cohesive energy, density, and viscosity, were compared to analyze the solid–liquid equilibrium behavior of WS-5. In addition, the thermodynamic properties of dissolution (ΔGsol, ΔHsol and ΔSsol) of WS-5 were calculated, and the results implied that the dissolution process of WS-5 was endothermic and entropy-driven.