THE ELECTROCATALYTIC INFLUENCE OF UNDERPOTENTIAL PB, TL AND BI ADSORBATES ON THE ELECTROCHEMICAL-BEHAVIOR OF 2,4-DINITROSORESORCINOL AND TETRAOXIME OF 1-CYCLOHEXENE-3,4,5,6-TETRONE ON PT AND AU

The electrochemical behaviour of 2,4-dinitrosoresorcinol (DNR) on Pt a nd Au electrodes modified by underpotentially-deposited heavy metal mo nolayers was studied in aqueous HClO4 solutions. At these modified ele ctrodes, DNR is reduced to 2,4-diaminoresorcinol. The reduction wave o f this eight-electron reaction is diffusion-controlled. This process p roceeds through hydroxylamine intermediates whilst an azoxy derivative is formed by a condensation reaction between DNR and the dihydroxylam ino intermediate. The reduction and oxidation of tetraoxime of 1-cyclo hexene-3,4,5,6-tetrone (TCT) was also studied on Pt surfaces covered b y heavy metal monolayers. The reduction of TCT is a 12-electron reacti on yielding phenylene-1,2,3,4-tetramine. The reduction of this cathodi c process also exhibits diffusion-controlled character. The oxidation of TCT is a four-electron reaction producing 1,2,3, 4-tetranitrosobenz ene which is rapidly converted to the tautomeric form benzobifuroxan.