Madder plant

Qumones are colored p benzoqumone for example is yellow Many occur natu rally and have been used as dyes Alizarin is a red pigment extracted from the roots of the madder plant Its preparation from anthracene a coal tar derivative m 1868 was a significant step m the development of the synthetic dyestuff industry... 

Alizarin. There is only one significant plant anthraquinone dye, alizariu [72-48-0] (Cl Natural Red 6, 8, 9,10, 11, and 12 Cl 75330). In ancient times, alizaria was the preferred red dye. Cloth dyed with it has been found in Egyptian tombs dating 6000 years ago. The dye is found in the madder plant, a member of the Rubiaceae family. In 1944 about 35 species of this plant were known (1), but the use of more sophisticated analytical methods led to the detection of many more species by 1984 the number had increased to 50 (2). Of these, tinctorum and R peregrina yield the greatest amount of dye,... 

Alizarin or l 2-dihydroxyanthraquinone is one of the most important dyes. Like indigo, the dye occurs in the plant (the madder root) as the glucoside of the leuco-compound. The cultivation of the madder plant, which, chiefly in southern France, extended over large areas, was brought to an end by the synthesis of the dye from the anthracene of coal-tar (Graebe and Liebennann, 1869). By distillation with zinc dust according to the method of Baeyer, these two chemists had previously obtained anthracene from alizarin. 

The British are coming, the British are coming cried Paul Revere. Well, he could hardly have missed them, decked out in their bright red coats. The attire of the British soldier tended to undermine military strategy, but the color had nothing to do with battle tactics. It had to do with economics. The British uniforms were required, by royal decree, to be dyed red in order to support British agricultural interests, specifically the cultivation of the madder plant (Rubia tinctorum). It was from the roots of this plant that the brilliant red dye known as alizarin was extracted. Alizarin was not produced in the colonies, and... 

Organic dyes like indigo, madder (source of red) and woad can easily attach themselves to cloth. Indigo dye is extracted from the leaves of the plant indigofera, and the red dye from the madder plant. Madder plant has yellow flowers and red root. The dye is extracted from the root. 

The fiber is first treated with metal salts (mordanted). Highly adhesive, basic metal compounds are formed on the fiber. These compounds are capable of producing insoluble colored complexes (lakes) with certain azo and anthraquinone derivatives. Alizarin is the best-known anthraquinone derivative for this process (see Section 2.3). It used to be isolated from the root of the madder plant but has now been replaced by the synthetic product. Suitable azo dyes contain, e.g., hydroxyl or carboxyl groups in the position ortho to the azo group on one or both of the aromatic nuclei. The shade of the dyeing depends on the type of metallic mordant used. Alizarin with aluminum or calcium salts produces the well-known Turkey red. 

The wide varity of anthraquinone dyes identified in various madder plants is not to be found in the dye insects American cochineal, kermes, Polish and Armenian cochineal. These insects contain two dyes whose constitutions are known and a third dye whose constitution has not yet been clarified. However, the fifth in the class of dye insects, lac dye, contains five water-soluble dyes ( = laccaic acids) and traces of three water-insoluble dyes. 

Turkey Red.—Alizarin is the chief constituent of the coloring matter Turkey red, which has been known since ancient times and which was obtained from the root of the madder plant, Rubia tinctorum L. The substance is of special interest because the determination of its constitution was one of the early triumphs of organic chemistry and because it was the first natural dye to be synthetically prepared. The name is derived from the oriental name for the madder, viz., alizari. In the madder root it is present as a glucoside known as ruberythric acid, which, on hydrolysis by fermentation or by boiling with acids, yields glucose and alizarin. Alizarin is a solid which sublimes as orange red needles, m.p. 289°, insoluble in water but slightly soluble in alcohol. 

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 ... 

In the Renaissance, the illuminator s reds included cinnabar (mercuric sulfide), a substance well-known to alchemists. Vermilion red was extracted from Brazilwood, and a purplish red was derived from the root of the madder plant.112 The sap of the shrub Pterocarpus draco produced a popular red called dragon s blood. Yarn had it that dragon s blood was the co-mingled blood of an elephant and a dragon who had slain one another in battle.113 Blues were obtained from stones (azurite, lapis lazuli) and from plants (the seeds of turnsole or Crozophora in alkaline solution).114 Lapis lazuli must have seemed nearly as mysterious and difficult to obtain as dragon s blood, since at that time it was found only in a mine in north-east Afghanistan. 

Rubine n. Pertaining to blue shade red, probably derived from the Latin word rubia for the madder plant from which madder lake (Alizarin Red), a blue shade red, was originally made. The name of the bluish red colored gem, the ruby, would appear to be similarly derived. 

All the dyestuffs mentioned so far had no natural counterparts. However, in 1869 Perkin in England and Heinrich Caro (1834-1910) in Germany independently discovered a method of synthesising alizarin, the natural dye of the madder plant, which had been used since antiquity. The starting material for the synthesis was the hydrocarbon anthracene. This is present in the least volatile fraction of coal tar, for which hitherto there had been very little use. Its value now increased enormously. 

The advent of cheap synthetic alizarin resulted in the cessation of the cultivation of the madder plant. Some years later, most indigo plantations also became redundant. Natural indigo is a mixture obtained by fermentation and oxidation of the plant extract, and the principal coloured component is indigotin. Synthetic indigotin was available from the 1890s. 

Meyer plots the atomic volume (atomic weight divided by density) of each element against its atomic weight and shows that elements whose chemical properties are similar appear in similar positions on the waves of the curve. Russian chemist Dmitry Mendeleyev publishes the first periodic table for chemical elements. He writes, The properties of the elements are in periodic dependence upon their atomic weight. His table shows how the elements are related to each other and how increasing atomic weight affects their chemical reactivities. Gaps in the table indicate elements yet to be discovered and predict their properties. Mendeleyev coins the term transition element British chemist Sir William Perkin develops synthetic alizarin for manufacture from the madder plant. 

Evidence to support this proposal has been obtained by Burnett and Thomson in work with the madder plant (Rubia tinctorum). 2-[ C]-Mevalonic acid was administered to this plant and was incorporated into a series of anthraquinone metabolites such as alizarin (101), purpurin (124) and pseudopurpurin (102). Degradation of the quinones to phthalic acid showed that all the radioactivity was confined to ring C. Decarboxylation of pseudopurpurin (102) gave purpurin (124) containing one half of the total radioactivity and this is in agreement with the hypothesis outlined above namely that ring C of these quinones is derived by cyclisation of a precursor such as lapachol (122). Burnett and Thomson s observations imply that the two methyl groups in the precursor (122)... 

Fig. 5.5 Components of the root of the madder plant, Rubia tinctorum...

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