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Ten nitrophenyl N-glycosides have been studied electrochemically in neutral (at pH 7) water–organic solutions by cyclic voltammetry using static mercury drop electrode. For all compounds under investigation the two electrochemical processes have been observed: the four-electron irreversible reduction of their nitro groups to the corresponding phenylhydroxylamine derivatives, as well as the two-electron quasi-reversible process between phenylhydroxylamine and nitroso derivatives. For three compounds the additional electrochemical processes have been also observed, which can be connected with the formation of azoxybenzene derivatives. The potentials of both redox processes: a two-electron quasi-reversible RNHOH/RNO (Ef) and four-electron irreversible RNO2/RNHOH (Epc(I)) systems have been determined and discussed according to crystal structures of selected compounds. Ef and Epc(I) depended strongly on the positive mesomeric effect (caused by glycosidic nitrogen atom), as well as on the intramolecular hydrogen bond between electroactive nitro group and the hydrogen atom at the glycosidic atom observed in N-o-nitrophenyl-2,3,4,6-tetra-O-acetyl-β-D-glucopyranosylamine. Moreover, the chirality of selected reactants has had the pronounced effect on the Epc(I). Copyright © 2011 John Wiley & Sons, Ltd. |
