Ibuprofen solubility in pure organic solvents and aqueous mixtures of cosolvents: Interactions and thermodynamic parameters relating to the solvation process

• The solubility data allow us to obtain the information on the interactions that occur in the process of solvation.
• For the seven pure n-alcohols analyzed, as the amount of carbon atoms increases, the Ibu's solubility decreases.
• The analysis of solution processes in binary aqueous systems shows a non-ideal behavior and an influence of solvent–solvent interactions.
• The process of solution in water and in water-rich cosolvent mixtures studied is driven by the entropic term.

The solubility of Ibu in fifteen pure solvents and in eight aqueous–organic cosolvent mixtures was determined. The results obtained indicate that Hildebrand's solubility parameter of pure solvent, which accounts for the cohesive forces of the solvent, has a greater influence on the solubility of Ibu. In all the cosolvent mixtures analyzed, the solute was preferentially solvated by the organic cosolvent. For aqueous binary mixtures formed by ethanol, ethylene glycol and propylene glycol, the enthalpy, entropic and Gibbs free energy changes involved with the solvation process were determined. In the three systems analyzed, it can be seen that the energy of formation of the cavity decreases as the polarity of the solvent decreases by increasing the amount of organic cosolvent, which, in this case, favors solute–solvent interactions. However, it was noted that there is a significant interaction between water and the organic cosolvent, which has a marked influence on the solvation process.