Studies of the electrochemical reduction of some dinitroaromatics

The electrochemical reduction of a series of dinitroaromatics, along with one trinitro compound, has been investigated at a glassy carbon electrode in N,N-dimethylformamide. The separation between the two standard potentials for the reduction, E°₁ − E°₂, has been determined and discussed in terms of the structures of the compounds. cis-4,4′-Dinitrostilbene was shown to undergo redox-catalyzed isomerization to the trans isomer. This was demonstrated with partial controlled potential electrolysis followed by chromatographic analysis of the solution. It was also found that redox-catalyzed isomerization could adequately account for the voltammetric behavior. The anion radicals of 3,5-dinitropyridine and 1,3,5-trinitrobenzene undergo reversible dimerization reactions. The rate and equilibrium constants for the dimerization were determined by simulation of the voltammograms of these two compounds and also by simulation of the voltammograms obtained with solutions from the one-electron controlled potential reduction, that is, solutions of the dimer. The equilibrium constants for dimerization were also determined by electron paramagnetic resonance spectroscopy.