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wherein R 1 is an aliphatic or aromatic optionally substi› tuted organic radical; and 2 

wherein R is an aliphatic or aromatic optionally substi- tuted organic radical. 

In various embodiments the aqueous catholyte of the instant invention comprises water and, completely or par› tially dissolved therein, an ester of nitric acid that is repre- sented by the general formula: 

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wherein R is an aliphatic or aromatic optionally substi› tuted organic radical. 

In various embodiments the aqueous catholyte of the instant invention comprises water and, dissolved therein, a sulfur-containing organic compound such as sulfonic acid or an amide of sulfonic acid (i.e., a sulfonamide). For instance, a sulfonic acid represented by the general formula 

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wherein R represents an organic aliphatic or aromatic group. Or sulfonamides represented by the general formula 

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wherein R 1 , R $^{2}$=an organic aliphatic or aromatic group. 

Suitable sulfonic acids include MES (2-(N-Morpholino) ethanesulfonic acid), MOPS (3-(N-Morpholino)propanesul› fonic acid), BES (N,N-Bis(2-hydroxyethyl)-2-aminoethane- sulfonic acid), TES (2-[ (2-Hydroxy- l, 1-bis(hydroxymethyl) ethyl)amino ]ethanesulfonic acid), TAPSO (2-Hydroxy-3- [ tris(hydroxymethyl)methylamino ]-1-propanesulfonic acid), N-[Tris(hydroxymethyl)methyl]-3-amino-2-hydroxy› propanesulfonic acid), HEPPS ( 4-(2-Hydroxyethyl)-1-pip› erazinepropanesulfonic acid), CHES (2-(Cyclohexylamino) ethanesulfonic acid), 3-Aminobenzenesulfonic acid; for example MES, MOPS, and HEPPS. 

Suitable sulfonamides include o-, m-, p-aminobenzene› sulfonamides, o-, m-, p-methylbenzenesulfonamides, o-, m-, p-cyanobenzenesulfonamides, 4,4’-diaminobenzenesulpha› nilide. 

In various embodiments the aqueous catholyte of the instant invention comprises water and, dissolved therein, a phenol. Phenols are organic compounds containing an hydroxyl group directly attached to an aromatic carbon atom, and may be represented by the general formula 

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Wherein R 1 , R 2 , R 3 , R 4 , R $^{5}$=H, OH, CH$_{3}$ , C$_{2}$H$_{5}$ , C$_{3}$H$_{7}$ , NH$_{2}$ , NO$_{2}$ , CN, COOH, SO$_{3}$H, C(R)=O, F, Cl, Br, I, CF$_{3}$ , NR$_{3 }$ +, COOR, CONH$_{2}$ , CC1$_{3}$ , OR, NR$_{2}$ ; and R represents H, or an aliphatic or aromatic organic radical. 

Phenol acidity and electrooxidation potential both depend on its substituents. The oxidation potential of substituted phenols becomes more positive, and pKa values become more negative with an increase of Hammett’s constant value of the corresponding substituent. In other words, the direct electrochemical oxidation of substituted phenol with an electron-withdrawing group is more difficult, and acidity is higher than that of substituted phenol with an electron› donating group. 

Particularly suitable phenols include resorcinol, 2-meth- ylresorcinol, gallic acid, 4-nitrocathecol, 4-hydroxybenzoic acid, 2-nitroresorcinol; for example, a-resorcylic acid, a-re› sorcylonitrile. 

In various embodiments the aqueous catholyte of the instant invention comprises water and, dissolved therein, an aminium salt formed with inorganic acid. For instance, a salt represented by the following general formula (HNR $^{1 }$R $^{2}$R 3 t x-, wherein x- represents an inorganic acid residue and R 1 , R 2 , R 3 may represent hydrogen atom, and at least one of them represents an aliphatic or aromatic optionally substi› tuted organic radical. The aminium salt is preferably selected from chloride, sulfate, perchlorate salts, and even more preferably is a nitrate. 

Particularly suitable such salts include aniline nitrate, diethylenetriamine nitrate, ethanolamine nitrate, 2-methyl- 1-pyrroline nitrate, methoxyamine nitrate, N-methoxymeth› ylamine nitrate, 1-benzoylpiperazine nitrate, N-methylhy› droxylamine nitrate, 2-aminocyanopropane nitrate, N,N› diethylcyanoacetamide nitrate, dimethylaminoacetonitrile nitrate, 2,2-diethylaminopropionitrile nitrate, 2-amino-2- cyanoproapne, piperazine dinitrate, N,N-dimethylethylene› diamine dinitrate, N-ethylmorpholine nitrate, and trietha› nolamine nitrate. 

Alternatively, the aminium salt may be based on a N-het- erocyclic aromatic compound such as imidazole. Particu› larly suitable such salts include imidazolium nitrate, 2-meth› ylimidazolium nitrate, 4-hydroxymethyl imidazolium nitrate, 4-hydroxybenzimidazolium nitrate, 4-methoxyben- zimidazolium nitrate, 4-(N-methylacetamido)pyridinium nitrate, o-, m-, p-methylpyridinium nitrate, o-, m-, p-ethyl› pyridinium nitrate, 2-methoxypyridinium nitrate, 3-methoxypyridinium nitrate, 3-hydroxypyridinium nitrate, 4-hydroxypyridinium nitrate, 3-fluoropyridinium nitrate, 3-bromopyridinium nitrate, 3-sulfoxypyridinium nitrate, 3-aminopyridazinium nitrate, 3-carboxypyridinium nitrate, 4-methoxypyridazinium nitrate, and 2-amino-4,6-dimethyl pyrazinium nitrate; for example, imidazolium nitrate. 

In yet other alternative embodiments the aminium salt may be an ammonium salt. For instance, that which is represented by the general formula (NH$_{4 }$ +)x-, wherein x- is an acid residue. 

