POLAROGRAPHIC AND ELECTROCHEMICAL STUDIES OF SOME AROMATIC AND HETEROCYCLIC NITRO-COMPOUNDS .5. POLAROGRAPHIC-REDUCTION OF CYANO-NITROPYRAZOLES AND CARBOXAMIDO-NITROPYRAZOLES

Reduction of the nitro group in 1-alkyl-4-cyano-5-nitropyrazoles follows a pattern similar to that of 1-alkyl-5-nitropyrazoles, involving the sequence H+, e, H+, e, 2e, 2H+. On the other hand, the sequence of proton and electron transfers in the reduction of the nitro group in 1-alkyl-3-nitro-4-cyanopyrazoles differs from that in 1-alkyl-3-nitropyrazoles. Similarly, the reduction of 4-cyano-3(5)-nitropyrazole differs from that of 3(5)-nitropyrazole, even when both of these reductions are affected by the dissociation of the NH group with pK(B) = 6.26 and 9.81, respectively. Similarly, the behavior of 1-alkyl-4-carboxamido-5-nitropyrazoles resembles that of 1-alkyl-5-nitropyrazoles, but that of 1-alkyl-3-nitro-4-carboxamidopyrazoles is different from that of 1-alkyl-3-nitropyrazoles. In 1-alkyl-4-carboxamido-5-hydroxylaminopyrazoles, the carboxamido group is reduced in a two- and four-electron process, but the low absolute value of the limiting current of wave i2 indicates the presence of competitive side reactions.