6-Phenyl-3(2H)-pyridazinone dissolved in some aqueous co-solvent mixtures of alcohols: Equilibrium solubility, solvent effect and preferential solvation

Abstract

The saturated solubility of 6-phenyl-3(2H)-pyridazinone in aqueous co-solvent mixtures of methanol, ethanol, isopropanol and ethylene glycol (EG) was determined through experiment by employing the saturation shake-flask method at temperatures from 278.15 to 318.15 K and local atmospheric pressure. For all the co-solvent mixtures, the maximum value of solubility was observed in neat methanol (ethanol, isopropanol or EG). The 6-phenyl-3(2H)-pyridazinone solubility in mole fraction scale was well correlated by using the Jouyban-Acree model and van’t Hoff-Jouyban-Acree model, obtaining the values of relative average deviations smaller than 3.98%; and root-mean-square deviation, lower than 7.81 × 10−5. The local mole fractions of methanol (ethanol, isopropanol or EG) and water nearby the 6-phenyl-3(2H)-pyridazinone were quantitatively calculated by means of the Inverse Kirkwood-Buff integrals method. 6-Phenyl-3(2H)-pyridazinone was preferentially solvated by the solvent of water in water-rich compositions; while within the regions of co-solvent-rich and intermediate compositions, 6-phenyl-3(2H)-pyridazinone was preferentially solvated by the solvent of methanol (ethanol, isopropanol or EG). The mole fraction solubility was fitted by using the Kamlet and Taft linear solvation energy relationships to inspect the key factors describing solvent effect. The variation in cavity formation energy and hydrogen-bond acidity played the chief role upon the 6-phenyl-3(2H)-pyridazinone solubility in aqueous solutions of methanol and ethanol; and the hydrogen bond acidity and dipolarity/polarizability term, in the aqueous of mixtures isopropanol and EG .