Interfacial behaviour at the mercury/aqueous solution interface of derivatives of benzensulfonamide and benzoic acid. A theoretical study of the role of the substituents on a common molecular framework.

The adsorption process at the Hg aq. soln. interface (NaClO4 + NaOH, pH 12) of a series of benzenesulfonamides and benzoic acids is interpreted using some calcd. structural indexes (superdelocalisability, electron d., shape of HOMO). The relations among the indexes and the adsorption free energy (at const. potential) indicate that the combined effects on the local electronic properties of the mol., induced by the different substituents, greatly affect the interfacial behavior, mainly when substitution on the amidic nitrogen of benzenesulfonamides is involved. This fact is confirmation that in the biol. action of the pharmacol. active compds., a possible adsorption step can be regarded as the one limiting the biol. activity.