Mauveine

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Image:Mauveine-A.PNG
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Image:Mauv2.jpg Mauveine, also known as aniline purple, was the first synthetic organic dye. The chemical name is 3-amino-2,±9-dimethyl-5-phenyl-7-(p-tolylamino)phenazinium acetate. The formula is C₂₆H₂₃N₄⁺X^- (mauveine A) and C₂₇H₂₅N₄⁺X^- (mauveine B, see below).

It was discovered serendipitously in 1856 by an 18-year old William Perkin, who was trying to synthesize the anti-malaria drug quinine as a challenge offered by his professor, August Wilhelm von Hofmann. In one of his attempts to make quinine, Perkin oxidized aniline using chromic acid. Under these conditions, the aniline reacted with toluidine impurities in it to produce a black solid, a fairly common result in "failed" organic syntheses. However, while trying to clean out his flask, Perkin discovered that some component of the black solid dissolved in alcohol to give a purple-coloured solution, which proved to be an effective dye for silk and other textiles.

Perkin patented the new dye and the next year, he opened a dyeworks at Greenford on the banks of the Grand Union Canal in London in order to mass produce it. Mauve became highly fashionable—in 1862, Queen Victoria appeared at the Royal Exhibition in a mauve silk gown. Mauve fell out of fashion in the late 1860s to newer synthetic colours, but not before making Perkin's fortune and birthing the synthetic chemical industry. Later work on chemical dyes also led to the (accidental) development of modern chemotherapy (see Sulfonamide). Image:Rees1.jpg Incidentally, the actual molecular structure of mauveine proved quite difficult to determine and was not known with certainty until 1994 <ref>O. Meth-Cohn, M. Smith, "What did W. H. Perkin actually make when he oxidised aniline to obtain mauveine?", J. Chem. Soc. Perkin 1, 1994, 5-7. DOI: 10.1039/P19940000005. This reference is not Open Access.</ref>. It is actually a (variable) mixture of two related aromatic compounds, mauveine A, shown above at right, and mauveine B, which has one additional methyl group. As Perkin showed in 1879 <ref>W. H. Perkin, "On mauveine and allied colouring matters", J. Chem. Soc. Trans., 1879, 717-732. DOI: 10.1039/CT8793500717. This reference is not Open Access.</ref>, mauveine B is related to the Safranines by oxidative/reductive loss of the p-tolyl group. In fact, Safranine itself is a 2,8-dimethyl phenazinium salt, whereas the parasafranine produced by Perkin must be presumed to be the 1,8-(or 2,9) dimethyl isomer.

The InChI identifier for mauveine B is [[InChI=1/C27H24N4/c1-17-9-11-20(12-10-17)29-21-13-19(3)27-26(15-21)31(22-7-5-4-6-8-22)25-16-23(28)18(2)14-24(25)30-27/h4-16H,1-3H3,(H2,28,29)/p+1]]
The InChI identifier for mauveine A is [[InChI=1/C26H22N4/c1-17-8-10-19(11-9-17)28-20-12-13-23-25(15-20)30(21-6-4-3-5-7-21)26-16-22(27)18(2)14-24(26)29-23/h3-16H,1-2H3,(H2,27,28)/p+1]]
The InChI identifier for safranine is [[InChI=1/C20H18N4/c1-12-8-17-19(10-15(12)21)24(14-6-4-3-5-7-14)20-11-16(22)13(2)9-18(20)23-17/h3-11H,1-2H3,(H3,21,22)/p+1]]
The InChI identifier for parasafranine is [[InChI=1/C20H18N4/c1-12-9-17-18(11-16(12)22)24(15-6-4-3-5-7-15)19-10-14(21)8-13(2)20(19)23-17/h3-11H,1-2H3,(H3,21,22)/p+1]]

Rotatable 3D models of mauveine are available using Jmol

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