A Synthesis of Pseudo-Mauveine and a Homologue

Abstract

Treatment of N-phenyl- p-phenylenediamine and two equivalents of aniline with potassium dichromate in hot water acidified with a small amount of sulfuric acid gives 3-phenylamino-5-phenyl-7-aminophenazinium sulfate (pseudo-mauveine). The oxidation of N-phenyl- p-phenylenediamine and o-toluidine with potassium dichromate in water with a small amount of sulfuric acid gives 3-phenylamino-5-( o- toluyl)-7-amino-8-methylphenazinium sulfate. Oxidation of aniline and ( o or p) toluidine only gave small quantities of mauveine chromophores. Oxidation of p-toluidine gives a known dimer which gives a purple coloured solution in acid. A hypothesis is described in which N-phenyl- p-phenylenediamine may have been involved in mauveine synthesis in the nineteenth century.