Nitro-aromatic compounds reduction potential effect

Effect of the Reduction Potential of the Nitro-Aromatic Compound... 

In the electroreduction of aromatic hydrocarbons, nitro compounds, and quinones in aptotic solvents, the first step is the transfer of an electron from the electrode to form a radical anion. Once the radical anion is formed, electron repulsion will decrease the facility with which a second electron transfer occurs. But solvation and ion pairing diminish the effect of electron repulsion and tend to shift the reduction potential for the addition of the second electron to more... 

Newkome and coworkers have modified their diaminoanthraquinone-containing dendrimers [56] by incorporating a redox-active aromatic nitro-containing group into the internal structure of the dendrimer. These compounds were studied by cyclic voltammetry, and it was determined that the presence of the nitro group had a significant effect on the redox process of the AQ moiety, causing the peak potential of the AQ reduction to shift 100 mV in the positive direction [72]. 

Amidine derivatives are effective dehalogenation inhibitors for the chemoselective hydrogenation of aromatic halonitro compounds with Raney nickel catalysts. The best modifiers are unsubstituted or N-alkyl substituted formamidine acetates and dicyandiamide which are able to prevent dehalogenation even of very sensitive substrates. Our results indicate that the dehalogenation occurs after the nitro group has been completely reduced i.e. as a consecutive reaction from the halogenated aniline. A possible explanation for these observations is the competitive adsorption between haloaniline, nitro compound, reaction intermediates and/or modifier. The measurement of the catalyst potential can be used to determine the endpoint of the desired nitro reduction very accurately. 

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. 

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