Mauveine

Mauveine, also known as aniline purple and Perkin's mauve, was the first synthetic organic chemical dye, discovered serendipitously in 1856. 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 (C₂₆H₂₃N₄⁺X⁻) incorporates 2 molecules of aniline, one of p-toluidine, and one of o-toluidine. Mauveine B (C₂₇H₂₅N₄⁺X⁻) incorporates one molecule each of aniline, p-toluidine, and 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.

skeletal formula of mauveine A

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