N,N-Dimethylphenylenediamine (dimethyl-4-phenylenediamine) is an organic compound with the formula . It is one of the phenylenediamines, a class of compounds that have long attracted attention for their redox properties. This diamine is, for example, easily oxidized to a deep red radical cation, which is called Wurster's Red. The related Wurster's Blue cation has four N-methyl groups
Dimethyl-4-phenylenediamine is prepared by the nitration of dimethylaniline followed by reduction of the resulting 4-nitrodimethylaniline. A variety of methods have been examined.
Dimethyl-4-phenylenediamine can be converted to methylene blue by reaction with dimethylaniline and sodium thiosulfate in several steps:
It reacts with carbon disulfide to give the corresponding mercaptobenzothiazole:
Casmir Wurster discovered tetramethylphenylenediamine and its easy oxidation. Subsequent work revealed the variety of redox properties of the phenylenediamines.