Expected and unexpected products from reacting Sanger’s reagent with p-phenylenediamine

Abstract

p-Phenylenediamine reacts with Sanger’s reagent in hot ethanol to give the expected mono- and di-substitution products, but in ethanol at room temperature, it gave exclusively 2-nitro-5-fluorophenyl- p-phenylenediamine, where a hydrogen atom is displaced by attack at an activated, unsubstituted position. The reactions of p-phenylenediamine and aniline with Sanger’s reagent were compared in the cheap, ‘green’ solvent ethanol.