Exploring the structure, thermophysical properties, and solvent capacity of the pure cinnamyl alcohol, and its hydrophobic eutectic mixtures with thymol.

Eco-sustainable alternative solvents, particularly eutectic mixtures, constitute a key platform within green chemistry. In this study, thermophysical properties of pure cinnamyl alcohol and cinnamyl alcohol:thymol mixtures were measured, modelled, and discussed. The structure and solvent capacity of the mixtures were also analyzed. Nuclear magnetic resonance experiments showed prevalence of the hydrophobic intermolecular interactions and minimal aggregation. Experimentally measured densities, surface tensions, and viscosities were below 1050 kg·m-3, 43 mN·m-1, and 30 mPa·s, respectively, and decreased as the thymol mole fraction increased. A predominant parallel orientation of adjacent dipoles was also observed. The solubility of the active pharmaceutical ingredients studied in cinnamyl alcohol:thymol eutectic solvents was much higher than in water. Except for carvedilol, the solubility (in mole fraction) increased with the cinnamyl alcohol ratio. Overall, the results identify pure cinnamyl alcohol and cinnamyl alcohol:thymol mixtures as promising eco-friendly solvents with significant potential for improving the solubility of poorly soluble pharmaceuticals.