SOLVATIONAL BEHAVIOR OF SOME SUBSTITUTED BENZOIC-ACIDS IN ETHANOL-WATER MIXTURES AT 298.15 K

The effect of substitution on the solubility and dissociation constant s for the reaction HA half arrow right over half arrow left H+ + A-(HA = substituted benzoic acids) have been studied from the measurements of pH and solubilities of substituted benzoic acids in ethanol + water mixtures (0-100 wt%). The changes in the solubility values depend on the hydrophobic character and the dielectric constant of the solvent m edium. The free energies of transfer for anions have been determined f rom DELTAG(t)-degrees(dissn.) = DELTAG(t)-degrees(H+) + DELTAG(t)-degr ees(A-) - DELTAG(t)-degrees(HA) using the previously determined values of DELTAG(t)-degrees(H+). The results are discussed in the light of s olute-solvent interactions.