Electrochemical conversion of α-nitrobenzylic compounds into the corresponding oximes—Part 2. Macroscale electrolyses

Electroréduction de dérivés dinitrés aromatiques. V. influences du matériau d'électrode et de systèmes rédox sur les réductions du 4,4′-dinitrodibenzyle et de l'acide 4,4′-dinitrostilbène-2,2′-disulfonique

This work concerns the electrochemical and chemical reductions of 4,4′-dinitrodibenzyl and 4,4′-dinitrostilbene 2,2′-disulfonic acid under various experimental conditions. On the one hand, the electrochemical reduction is realized on Sn, monel, and Hg electrodes with or without the presence of a redox couple, and on the other hand, the chemical reduction is performed by mean of an electrochemically generated reducing agent (Sn0). According to the type of redox couple used (Ti3+/Ti4+ or sn0/sn2+), important changes in the nature and the ratio of reaction products are observed. The best conditions for obtaining di- or monoamines are defined, they correspond to 90% yield for the diamines, 70% and 50%, respectively, for 4-amino-4′-nitrodibenzyl and for 4-amino-4′-nitrostilbene-2,2′-disulfonic acid. The electrochemical behavior of the dinitro derivatives and of TiOSO4, TiCl4, and SnCl2, used as precursors of the redox couples is studied under conditions of macroscale electrolyses (5 N H2SO4–EtOH 50/50, 2.5 N H2SO4, and 10% HCl). Key words: 4,4′-dinitrodibenzyl, 4,4′-dinitrostilbene 2,2′-disulfonic acid, electrochemistry, reduction, Ti3+/Ti4+ and Sn0/Sn2+ redox systems.