POLAROGRAPHIC AND ELECTROCHEMICAL STUDIES OF SOME AROMATIC AND HETEROCYCLIC NITRO-COMPOUNDS .6. POLAROGRAPHIC, VOLTAMMETRIC, AND CONTROLLED POTENTIAL REDUCTION OF ORTHO-NITROBENZALDEHYDE ANTHRANIL

In acidic media, at pH < 7, the nitro group, in ortho-nitrobenzaldehyde (1) is reduced in a four-electron step to ortho-formylphenylhydroxylamine (II). The protonated form of II is reduced by two electrons to ortho-aminobenzaldehyde (IV), which is further reduced in a two-electron process to ortho-aminobenzylalcohol. At pH > 7, the arylhydroxylamine (II) condenses to form a nitrone, which is further reduced in two two-electron waves, corresponding to the cleavage of the N-0 bond and reduction of the azomethine bond. At pH 7, formation of anthranil (III) from II is a relatively slow process: in cyclic voltammetry (CV) and d.c. polarography, II is further reduced to IV; in controlled potential electrolysis at a mercury pool electrode, the same products are obtained at 0-degrees-C, but at 25-degrees-C, III is the predominant product.