Studies on the distribution of N-phenylanthranilic acid in two-phase system: Aromatic solvent–water

Abstract

The detailed description of equilibria of N-phenylanthranilic acid in the aqueous solutions and in the two-phase systems: aromatic solvent–aqueous solution were obtained. The isoelectric point, pH I, the dissociation constants of the protonated form, K a1, and the neutral form, K a2, in the aqueous solutions were determined from the apparent ionization constant in methanol–water solutions of various proportions by extrapolation to zero co-solvent using Yasuda–Shedlovsky procedure. On the basis of the spectrophotometric investigations, the values of the distribution ratio, D, of N-phenylanthranilic acid in the two-phase systems: aromatic solvent (benzene, ethylbenzene, toluene, chlorobenzene, bromobenzene)–aqueous solution were obtained. Employing the results of the potentiometric titration in the two-phase systems: aromatic solvent–aqueous solution, and using models of singular and multistep equilibria the values of the distribution constants, K D, dimerization constants, K dim, were calculated. The significant influence of the polarity of the applied aromatic solvents and pH of the aqueous phase on the percentage of the particular forms of N-phenylanthranilic acid in the two-phase systems was proved.