Mauveine

Mauveine, also known as aniline purple and Perkin's mauve, was one of the first synthetic dyes. It was discovered serendipitously by William Henry Perkin in 1856 while he was attempting to synthesise the phytochemical quinine for the treatment of malaria. It is also among the first chemical dyes to have been mass-produced. Mauveine is a mixture of four related aromatic compounds differing in number and placement of methyl groups. Its organic synthesis involves dissolving aniline, p-toluidine, and o-toluidine in sulfuric acid and water in a roughly 1:1:2 ratio, then adding potassium dichromate. Mauveine A () incorporates 2 molecules of aniline, one of p-toluidine, and one of o-toluidine. Mauveine B () incorporates one molecule each of aniline, p-toluidine, and two of o-toluidine. In 1879, Perkin showed mauveine B related to safranines by oxidative/reductive loss of the p-tolyl group. In fact, safranine is a 2,8-dimethyl phenazinium salt, whereas the parasafranine produced by Perkin is presumed to be the 1,8- (or 2,9-) dimethyl isomer. The molecular structure of mauveine proved difficult to determine, finally being identified in 1994. In 2007, two more were isolated and identified: mauveine B2, an isomer of mauveine B with methyl on different aryl group, and mauveine C, which has one more p-methyl group than mauveine A. File:Mauveine a skeletal org.svg|[[Skeletal formula]] of mauveine A File:Mauveine b skeletal org.svg|Skeletal formula of mauveine B File:Mauveine b2 skeletal org.svg|Skeletal formula of mauveine B2 File:Mauveine c skeletal org.svg|Skeletal formula of mauveine C In 2008, additional mauveines and pseudomauveines were discovered, bringing the total number of these compounds up to 12. In 2015 a crystal structure was reported for the first time. In 1856, William Henry Perkin, then age 18, was given a challenge by his professor, August Wilhelm von Hofmann, to synthesize quinine. In one attempt, Perkin oxidized aniline using potassium dichromate, whose toluidine impurities reacted with the aniline and yielded a black solid, suggesting a "failed" organic synthesis.