The peculiar electrochemical and physico-chemical behaviour of RSO2 substituted compounds can be attributed to the electronwithdrawing effect induced by sulphur atom, in particular the acidity of the nitrogen-bound hydrogen and the presence of a characteristic electrochemical reduction mechanism. Adsorption process at the mercury-aqueous solution of benzenesulfonamide derivatives and RSO2N-protected aminoacids is investigated and explained using some calculated structural indexes. The relations among these indexes and the adsorption free energy indicate that substitutions on the amidic nitrogen greatly affect the interfacial behaviour. The comparison of the reduction process of RSO2 protected aminoacids with that of the sulphonamide derivatives in protic and aprotic solvents has shown that these aminoacids, in neutral form, can be better considered as sulfonamides and their electrochemical parameters fit structural correlations with theoretical indexes, as LUMO energy and localized charges, in the same way shown by sulfonamide derivatives. Using these correlations, the role of the RSO2 moiety on the amidic acidity and on the electron transfer process has been discussed also on the basis of the calculated differences in total energy of dissociated and undissociated species. Theoretical indexes allow to investigate the electron route in the electrochemical reduction and the role of the substituents on nitrogen atom in determining mechanism and energetics of the electrochemical process.
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