THE REDUCTION-MECHANISM OF AROMATIC NITRO-COMPOUNDS IN AQUEOUS-MEDIUM .1. REDUCTION TO DIHYDROXYLAMINES BETWEEN PH-0 AND 5

The reduction of aromatic nitro compounds, RNO2, to their dihydroxylamines, RN(OH)2, was studied by cyclic voltammetry. It proceeds via electron-proton exchanges (nine-member square scheme). Between pH 0 and 5, the slow step is the reduction of the radical RNO2H. to the dihydroxylamine, first according to a H+e- (RNO2H.→ RNO2H+2→ RN(OH)2) then to an e-H+ (RNO2H.→ RNO2H-→ RN(OH)2) process. The global path between pH 0 and 5 is probably first e- H+ H+e-, then e- H+e- H+. © 1990.