Thermodynamic Modeling of the Solubility and Preferential Solvation of the Natural Product Vanillic Acid in Some Aqueous Mixtures of Alcohols at Different Temperatures

The solid–liquid equilibrium of vanillic acid (3) in solvent mixtures of 1-propanol (1) + water (2) and 2-propanol (1) + water (2) was estimated utilizing gravimetric method findings in the temperature range of 283.15–323.15 K. The solvency of vanillic acid depends on temperature and dissolvable mixtures, and it was determined through the van’t Hoff–Jouyban–Acree and Apelblat–Jouyban–Acree models. Normal relative deviations lower than 3% and root-mean-square deviations lower than 0.53 × 10–3 were obtained for reciprocal examinations. With the solubility data obtained in this study and the results from our previous work, we determined the particular solubility criteria (δx 1,3) of a characteristic phenolic compound, vanillic acid, in parallel solvent combinations of cosolvent (1) + water (2). The values of δx 1,3 changed nonlinearly with the codissolvable (1) dimension in the concentrated varied solvents. Vanillic acid was especially solvated by water in water-rich compositions, whereas in cosolvent-rich and intermediate compositions, it was preferentially solvated by the organic solvent in the mixtures studied. Vanillic acid was especially solvated by a cosolvent as a result of its positive δx 1,3 values. A positive δx 1,3 estimate can be clarified as high acidic behavior of vanillic acid particles in collaboration with hydrogen acceptors organized in a cosolvent.