No dye story would be complete without some mention of mauveine. It was first discovered in 1856 by a young chemist called William Henry Perkins, although it was not his intention!
His aim was to synthesise quinine, a drug extracted from tree bark and used as a preventative against malaria. Since very little was then known about the structure of quinine, or indeed any organic molecule, he took a stab in the dark and began by oxidising allyltoluidine1:
2C10H13N + 1ŻO2 ----> C20H24N2O2 + H2O
Since we now know the structures of both quinine and allyltoluidine, it is easy to see why it didn't work1. What he did notice, however, was a brown product. This was sufficiently interesting for him to investigate further, and he repeated the experiment, but with aniline extracted from coal tar instead. This resulted in a black product, which we now know to be Aniline Black. But when he extracted this with alcohol, he obtained a purplish product which he called Aniline Purple1,2.
When Aniline Purple was tested on silk at a dye works in Perth, Scotland, it gave a rich purple colour. He took out a patent on it and went into production2.
His triumph was not only due to fortuitous experimentation, but to his ability to investigate further and develop his discovery, and to scale up the production to industrial scale, thereby giving birth to the concept of industrial chemistry as we know it.
The discovery of Aniline Purple set off a furious race to find more dyes with similar compositions, using aniline as a starting point. These dyes were sometimes called as 'coal-tar' dyes due to the origin of aniline, and for a long time, all synthetic dyes were referred to as aniline dyes, regardless of their starting molecules2. All aniline dyes are basic in character (see Synthetic Textile Dyes)
For more information on the discovery of mauveine, click on the link below to go to the very first Molecule of the Month page.