Electroreduction nitro groups

Reduction of the cinnoline nucleus was a side reaction in the stannous chloride reduction of the nitro group in 4-carboxamido-3-nitrocinnoline, but was minimized by the careful use of just three equivalents of the reductant <84JOC289>. A mechanistic study of the electroreduction of benzo[c]-cinnoline has shown that the ArNHNAr radical is an intermediate which breaks down by disproportionation to give benzo[c]cinnoline and 5,6-dihydrobenzo[c]cinnoline. The latter is the product obtained after two-electron reduction by electrolysis at —1.1 V in aqueous medium <88JOC5781>. 

Electroreduction of nitro compounds is of considerable importance for electroorganic synthesis. Interesting catalytic effects were reported for the reduction of aromatic nitro compounds on Pt. Figure 11 shows that Ph, Tl, and Bi adlayers shift the half-wave potential positively by 100 to 300 mV. The catalytic effect was attributed to a change in the mechanism of the reduction of the nitro group from a catalytic hydrogenation on bare Pt to an electron-transfer mechanism on Pt/Mad, that is, a direct electron exchange between the nitro compound and the adatom-covered electrode surface, namely. 

The few pesticides investigated so far on BDD electrodes using voltammetric methods include some carbamate pesticides (carbaryl, " carbendazim ), and organophosphorus pesticides (parathion, methyl parathion, and fenamiphos ). Determination of the latter group is based on the reduction of the nitro group and thus these pesticides are among the few examples on utilization of BDD electrodes for electroreduction. Carbamate pesticides, the N-substituted esters of carbamic... 

Ag, Au, and Pt electrodes has been studied during the last two decades [55-61]. It was found that ad-atom layers of Pb, Tl, and Bi deposited at underpotentials have a strong influence on the performance of the above substrates for the nitro and nitroso group electroreduction, both in terms of the improvement of the catalytic activity and the catalytic selectivity of these electrodes. 

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