Alizarin, production

Perkin s dye synthesis was the beginning of the coal-tar dyestuffs industry. He later developed and manufactured magenta (violet dye) and alizarin (a red dye). The rapid acceptance of these dyes by fabric manufacturers was demonstrated by the fact that annual alizarin production reached 220 tons per year by 1871. At age 37 and a wealthy man, Perkin sold his commercial holdings and devoted the rest of his life to pure chemical research. 

Anthraquinone [84-65-1] has yet to be found in nature, although some of its substitution products have been known since antiquity (alizarin, kermes, cochineal, and lac dye). Of all the quinones found naturally, those derived from anthraquinone far exceed all others. Many of these are found in molds (2). 

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. 

Upon heating anthraquinone with fuming sulphuric acid at 160° for about 1 hour, the main product Is anthraquinone-p-sulphonic acid, which is isolated as the sparingly soluble sodium salt. The latter when heated imder pressure with sodium hydroxide solution and an oxidising agent (sodium or potassium chlorate) yields first the corresponding hydroxy compound further hydroxy-lation occurs in the a-position through oxidation by the chlorate and 1 2-di-hydroxyanthraquinone (alizarin) is formed. 

Prussia (in northern Germany) was industrializing and urbanizing so quickly that onlookers called it Europe s Wild West. Building on synthetic alizarin red, Germany institutionalized chemical research. Perkin and other English inventors had established companies to exploit a product, but German firms exploited the research process itself. 

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. 

The formation of indanthrone and flavanthrone, as well as alizarin, during the alkali fusion of 2-aminoanthraquinone can be explained mechanistically on the basis of the initial loss of a proton. The resulting anionic species can be represented as a resonance hybrid and is also tautomeric (Scheme 6.12). Primary 1-hydroxylation of 2-aminoanthraquinone is probably the first step in the formation of the alizarin by-product (compare Scheme 6.8). Such an attack may initiate the formation of flavanthrone [31 ]. It is also possible to envisage the formation of all three species by a radical mechanism [32]. 

For purification the crude product is boiled with glacial acetic acid (preferably in the extraction apparatus shown in Fig. 27). Fine red needles melting point 289°. Sublimation in a vacuum from a sausage flask is also to be recommended the sausage should be fixed low down and the bulb completely immersed in a nitrate bath (equal parts of potassium and sodium nitrates). Much poorer yields of alizarin are obtained by using an open round-bottomed flask at 189°-190°. 

The first quinoline derivative obtained by the process (a) was the dye alizarin blue (Prud homme, 1877). f -Nitroaliza,rin was heated with glycerol and sulphuric acid. The constitution of the product was established by Graehe ... 

The classical forerunner of metallizable hydroxyanthraquinones was alizarin (1), which was widely used in the production of very fast, bright red shades on cotton by the mordant technique (Section 58.1). Early studies by Pfeiffer140 demonstrated that metal complex formation involved the carbonyl group and the a-hydroxy group (208) rather than the two hydroxy groups and led to intensive research on metal complexes of 1 -hydroxyanthraquinones and related compounds such as 8-hydroxynaphthoquinone. This is the subject of a number of reviews3a Jc141 and will only be considered briefly here. 

Of the different commercial qualities of alizarin, some are composed of almost pure alizarin (dihydroxyanthraquinone), others of mixtures of this with ftavopurpurin and anlhrapurpurin (isomeric trihydroxyanthraqui-nones), and others almost solely of one or other or both of the two latter substances. Another isomeride of these, purpurin, is also a commercial product. 

Occasionally in the synthesis of phenols by this route oxidation products are formed. A particular example is provided by the alkali fusion of sodium anthraquinone-2-sulphonate during which a second hydroxyl group is introduced into the 1-position, forming the dyestuff alizarin (1) (cognate preparation in Expt 6.99). In the procedure described the oxidation step is promoted by the deliberate introduction of potassium chlorate as an oxidant. 

Erk developed a spectrophotometric procedure for the assay of atorvastatin, both for the bulk drug substance as well as for pharmaceutical formulations. The procedures are based on the reaction between the drug and bromocresol green, alizarin red, or bromophenol blue, which result in the production of ion-pair complexes (1 1). Beer s law was obeyed over the concentration ranges 5.0-53.0, 7.1-55.8, or 7.5-56.0 /ig/ml with bromocresol green, alizarin red, and bromophenol blue, respectively. The specific absorptivities, molar absorptivities, Sandell sensitivities, standard deviations, and the percent recoveries were evaluated. Atorvastatin was determined by measurement of its first derivative signal at 217.8 nm. 

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 color was so distinctive that Perkin wondered if the product could be used as a dye. In 1856, he sent samples of the chemical to a dyeing company, Pullars of Perth, who responded that the dye appeared to have commercial potential. Perkin immediately applied for a patent on the dye, which rapidly became very popular in Great Britain and especially in France. It was the French, in fact, who gave the dye the name by which it is now known, mauve (the French word for the plant from which the natural and similarly colored dye alizarin is produced). As a consequence of the dye s huge commercial success, the decade of the 1890s is now referred to as the Mauve Decade. 

With the influence of an artist friend interested in painting and dyes, he started to develop aniline purple (Tyrian purple) production, which he patented in 1856 and set up a factory for. The dyestuff industry soon flourished. In 1859, Emanuel Verguin prepared the important dye fuschine, which was subsequently produced in Basel. In 1869, Perkin patented the synthesis of the natural dye alizarin, at the same time as Caro, Lieberman, and Graebe did so in Germany. Later, moreover, Perkin prepared alizarin from anthracene, which had been... 

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