Effects of aliphatic substituents on the reduction of nitroanilines. I. Studies by d.c. polarography

The reduction of 2-methyl-5-nitroaniline (A) and 2,4-di-t-butyl-6-methyl-5-nitroaniline (B) was studied in the 1/1 water/ethanol mixture at various pH values. In acidic media A gives two waves corresponding to 4- and 2-electron transfer, resp., whereas B produces a single, 6-electron wave. In alk. solutions, both compounds undergo a 4-electron reduction, producing two pH-dependent waves. The first wave of B recorded at high pH values displays a kinetic character, in contrast to A which induces diffusion-controlled waves. The bulky aliphatic substituents strongly influence the electrochem. behavior of both aromatic nitro derivatives and the corresponding hydroxylamines.