Solubility of monobenzone in aqueous co-solvent mixtures of several alcohols: Determination, modelling and thermodynamic aspects analysis

Abstract

Investigation upon the solubility of monobenzone in aqueous co-solvent mixtures of isopropanol, n-propanol, ethylene glycol (EG) and ethanol was performed via a saturation shake-flask technique at temperatures from 283.15 K to 328.15 K under pressure of p = 101.2 kPa. Experimental solubility magnitude presented positive dependence upon the mass fraction of each co-solvent and temperature. The greatest solubility value on the mole fraction scale was observed in the neat co-solvents. The equilibrated solids with corresponding co-solvent mixtures were characterized through an X-ray power diffraction (XRD) technique, demonstrating the absence of polymorphic transformation or solvate formation. The Jouyban-Acree model was adopted to mathematically describe the monobenzone solubility data. The maximum magnitudes of RAD and RMSD were 3.17 × 10−2 and 7.64 × 10−4, respectively. The local mole fractions of isopropanol (n-propanol, EG or ethanol) and water adjacent monobenzone were quantitatively studied by the Inverse Kirkwood–Buff integrals method. The parameters of preferential solvation for the isopropanol (n-propanol, EG or ethanol) were positive in the isopropanol (n-propanol, EG or ethanol) mixtures in intermediate and alcohol-rich compositions, indicating that monobenzone was preferentially solvated by the isopropanol (n-propanol, EG or ethanol). Monobenzone mainly acted as a Lewis acid which interacted with proton-acceptor functional group of the alcohols. Furthermore, the analysis of linear solvation energy relationships was made with a suitable combination of the solvent polarity descriptors to reveal the nature of intermolecular interactions bringing about the solubility variation in the co-solvent mixtures.