Graebe and Liebermann

This serendipitous discovery marked the beginning of the synthetic dyestuffs industry, based on coal tar as its main raw material, which is, incidentally, a waste product from another industry, steel manufacture. The development of mauveine was followed by efficient syntheses of natural dyes such as alizarin in 1869 (Graebe and Liebermann, 1869), and indigo in 1878 (Bayer, 1878 Heumann, 1890). The synthetic production of these dyes marked the demise of the agricultural production of these materials and the advent of a science-based, predominantly German chemical industry. The present-day fine chemicals and specialties, e.g. pharmaceuticals, industries developed largely as spin-offs of this coal tar-based dyestuffs industry. 

In 1871 Graebe and Liebermann discovered that alizarin (6.2) could be applied to wool by mordant dyeing after sulphonation to produce the 3-sulphonic acid (6.28). This dye is still listed in the latest revision of the Colour Index as a commercial product [11]. Although many sulphonated polyhydroxyanthraquinones have been examined, few remain in current use. Another, and more important, classic dye that continues in commercial use as an acid dye is Cl Acid Blue 45 (6.29). This dye was discovered in 1897 by Schmidt and can be made from anthrarufin (6.13) by disulphonation, subsequent dinitration and reduction. The dye gives an attractive blue on wool with good all-round fastness properties. 

Synthesis, Graebe and Liebermann.— The determination the of constitution of alizarin and its synthetic preparation are both due largely to the work of Graebe and Liebermann in 1868. 

The remarkable thing is, that while there are ten possible di-brom or di-hydroxy anthraquinones, the particular one necessary was obtained by Graebe and Liebermann. The positions of the two hydroxyl groups were determined by Baeyer and Caro. When alizarin is heated pyro-catechinol, i-2-di-hydroxy benzene, is obtained. Also when pyro-catechinol is heated with ortho- hXhaXic acid and sulphuric acid alizarin results. This last synthesis is analogous to that of anthraquinone from benzene and o //io-phthalic acid (p. 796). 

Commercial Synthesis.—In their work Graebe and Liebermann... 

Industrial Importance.—The synthesis of alizarin by Graebe and Liebermann was the first case of a common natural dye being prepared in the laboratory. As the synthesis starts with anthracene, a substance obtained in good yields from coal tar, it affords at once a cheap commercial source for the synthetic preparation of a natural product. Hardly any synthesis that has been worked out in the laboratory has had such an immediate effect upon industry as this one, and in addition to this it exerted a strong influence upon similar syntheses of other dyes. In 1868 Turkey red was a very common and valuable dye and the growth of the madder plant, in France especially, was an important industry. In their original paper Graebe and Liebermann make this statement ... 

The synthesis of alizarin was first effected by Graebe and Liebermann in 1869. These chemists had already observed the formation of anthracene from natural alizarin by heating with zinc powder, and recognizing alizarin as a derivative of anthracene, attempted to convert anthracene into alizarin. This aim was accomplished by fusion of bibromanthraquinone with potash. In the same year Graebe, Liebermann, and Caro [14] discovered the formation of alizarin by melting anthraquinonesulphonic... 

There was a time when few naturally-occurring dyes w ere of greater importance than madder because of its extensive use for dyeing bright red shades. The best madder red was dyed in Turkey and, from this, the name Turkey Red ultimately became a general term for all comparatively fast dyeings in this colour. The active mordant dye in madder is Alizarin, extracted from the root of the plant which was cultivated extensively in southern Europe, the Middle East, and Asia. It w as demonstrated by Graebe and Liebermann in 1868 that Alizarin was 1 2 dihydroxyanthra-quinone, (3) ... 

Alizarin is the most well known anthraquinone of madder. In 1826 alizarin was first isolated from Rubia tinctorum by Colin and Robiquet [91]. In 1868 Graebe and Liebermann deduced the structure of alizarin by zinc dust destination. They verified their hypothesis by synthesis of alizarin. In 1869 they patented an improved chemical synthesis of alizarin. 

Based on alizarin s orange-red colour, Graebe and Liebermann presumed that alizarin must be a derivative of anthraquinone, although the position of the two hydroxy-groups was still unclear. Since oxidation of alizarin gave phthahc acid, this suggested that one benzenoid ring had to be unsubstituted. 

One year after the structure elucidation of alizarin, Heinrich Caro at BASF developed in collaboration with Graebe and Liebermann the following successful synthesis. Sulfonation of anthraquinone with oleum [56] gives in the absence of catalysts, on steric grounds, anthraquinone-2-sulfonic acid [57] as the main product. This intermediate is then subjected to an alkali melt under oxidative conditions. 

Anthracene, C14H10, was discovered in coal-tar by Dumas and Laurent. Limpricht obtained it by heating benzoyl chloride and water at 190° in a sealed tube and concluded that it was related to benzene. Graebe and Liebermann obtained it by heating alizarin with zinc dust and assigned to it the structural formula I with a para-bond ... 

Following Graebe and Liebermann (1868, see p. 789) Armstrong proposed a quinonoid theory of colour. He proposed a theory of benzene substitution, and a centric formula of benzene (see p. 804). His work with F. P. Worley on reaction velocities in the catalytic hydrolysis of cane sugar and esters by acids ... 

This representative historically relevant example, as with the industrial preparation of important dyes such as mauveine (Tyrian purple, 8) (1856, Perkin), alizarin (2) (1869, Perkin, Graebe and Liebermann) or indigo (9) (1890, Heumann) (Figure 1.5), illustrates the significant economical impact of aromatic substitution chemistry [15]. 

The cultivation of madder for dyeing purposes was once of great economic importance as can be seen from the value of the traditional madder industry in France which was around 1865 worth about 16 million US dollars per year. The synthesis of alizarin in 1869 by Graebe and Liebermann wiped out the madder industry in about ten years, with the revenues being transferred completely from France to Germany 50). 

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