Phenylenediamine

This compound is a common hair dye. Its use is being supplanted by other aniline analogues and derivatives such as 2,5-diamino(hydroxyethylbenzene and 2,5-diaminotoluene. Other popular derivatives include tetraaminopyrimidine and indoanilines andindophenols. Derivatives of diaminopyrazole give red and violet colors. In these applications, the nearly colourless dye precursor oxidizes to the dye.

PPD is also used as a developing agent in the C-41 color photographic film development process, reacting with the silver grains in the film and creating the colored dyes that form the image.