Solubility of 6-phenyl-4,5-dihydropyridazin-3(2H)-one in aqueous mixtures of Transcutol and PEG 400 revisited: Correlation and preferential solvation

Reported equilibrium mole fraction solubility values of 6-phenyl-4,5-dihydropyridazin-3(2H)-one (PDP-6) (3) in {Transcutol (1) + water (2)} and {PEG 400 (1) + water (2)} mixtures at five temperatures from T = (293.15 to 313.15) K were analyzed based on the Hildebrand solubility parameter of the respective aqueous mixtures. Cosolvency models for representing the equilibrium solubility of PDP-6 in both binary solvent systems at various temperatures were also provided for correlation/prediction purposes. Moreover, the preferential solvation parameters of PDP-6 in these aqueous-cosolvent mixtures at T = (298.15 and 313.15) K were determined by means of the “inverse Kirkwood-Buff integrals” (IKBI). PDP-6 is preferentially solvated by water in water-rich mixtures of {Transcutol (1) + water (2)} system but preferentially solvated by Transcutol in mixtures of 0.13 < x₁ < 1.00. In the former case this result could be due to hydrophobic hydration around the non-polar moieties of PDP-6. Otherwise, PDP-6 is preferentially solvated by PEG 400 in all the aqueous mixtures. Moreover, in the systems where preferentially solvation of PDP-6 by cosolvents are observed, these results could be due to the Lewis acidic behavior of PDP-6 in front of Transcutol or PEG 400 molecules because these cosolvents exhibit higher Lewis basic behavior than water.