The dissociation constants (pKa4) and thermodynamic parameters Gibb's free energies (DG) have been determined by a potentiometric pH titration of 8-hydroxyquinoline (oxine) in water at 25 to 50°C and for 24-methylquinoline in water and in aqueous binary mixtures of dioxane, ethanol (EIOH) and methanol (MeOH)at 25°C ± 0.l°C. The first and second dissociates constants of oxine have been analyzed and discussed with (DG)   thermodynamic parameters. The pK values and thermodynamic parameters of 2. methylquinoline have also been computed and discussed in term of solute-solvent interactions. The curves found in both the compounds are a part of a parabola and these follow quadratic equations. The results are correlated with dielectric contants of medium and discussed in term of solvent characteristics, solvent basicity and stabilization of conjugate acid for base by hydrogen bonding interaction in hypo-organic solvent media.


A W K KHANZADA ,H A B INDHAR ,