1.2- dihydroxyanthraquinone

Alizarin, dihydroxyanthraquinone (indicator) dissolve 0.1 g in 100 mL alcohol pH range yellow 5.5-6.8 red. 

Materials. Beside inorganic materials (eg, barium chloride/fluoride crystals, doped with 0.05% samarium), transparent thermoplasts are preferred for the PHB technique, eg, poly (methyl methacrylate) (PMAIA), polycarbonate, and polybutyral doped with small amounts of suitable organic dyes, organic pigments like phthalocyanines, 9-arninoacridine, 1,4-dihydroxyanthraquinone [81-64-1] (quinizarin) (1), and 2,3-dihydroporphyrin (chlorin) (2). 

Anthraquinone chemistry began in 1868 with the elucidation of the stmcture of the naturally occurring compound alizarin (1) (1,2-dihydroxyanthraquinone) [72-48-0] by C. Graebe and C. Liebermann. 

In 1901, mercury cataly2ed a-sulfonation of anthraquinone was discovered, and this led to the development of the chemistry of a-substituted anthraquinone derivatives (a-amino, a-chloro, a-hydroxy, and a,a -dihydroxyanthraquinones). In the same year R. Bohn discovered indanthrone. Afterward flavanthrone, pyranthrone, and ben2anthrone, etc, were synthesi2ed, and anthraquinone vat dyes such as ben2oylaniinoanthraquinone, anthrimides, and anthrimidocarba2oles were also invented. These anthraquinone derivatives were widely used to dye cotton with excellent fastness, and formed the basis of the anthraquinone vat dye industry. 

Dihydroxyanthraquinone. This anthraquinone, also known as quinizarin [81-64-1] (29), is of great importance in manufacturing disperse, acid, and vat dyes. It is manufactured by condensation of phthalic anhydride (27) with 4-chlorophenol [106-48-9] (28) in oleum in the presence of boric acid or boron trifluoride (40,41). Improved processes for reducing waste acid have been reported (42), and yield is around 80% on the basis of 4-chlorophenol. 

Diaminoanthraquinone and Related Compounds. Leuco-l,4-diaminoanthraquinone [81-63-0] (leucamine) (32) is an important precursor for 1,4 diaminoanthraquinone [128-95-0] (33) and is prepared by heating 1,4-dihydroxyanthraquinone (29) with sodium dithionite in aqueous ammonia under pressure. 

Anthraquinone-a,a -disulfonic acids and Related Compounds. Anthraquinone-a,a -disulfonic acids and their derivatives are important intermediates for manufacturing disperse blue dyes (via 1,5-, or 1,8-dihydroxyanthraquinone, or 1,5-dichloroanthraquinone) and vat dyes (via... 

For years this was the process used to manufacture alizarin (19) although it was claimed that a more economical process would result if 2-chloroanthraquinone was used instead of silver salt (20). In 1870, the market price for 100% synthetic alizarin was 200 German marks, but by 1912 it had fallen to 5—6 marks, thereby sounding the death of natural alizarin (21). Also, dyers welcomed synthetic alizarin since it was 100% 1,2-dihydroxyanthraquinone natural alizarin always contained varying amounts of other polyhydroxyanthraquinones. 

A chemical process occurs involving the formation of a new substance with corresponding energetic ground state N (Fig. 14, 15/V). For instance, on aluminium oxide or silica gel layers in the presence of oxygen, anthracene initially yields anthra-quinone, that is then oxidized further to yield 1,2-dihydroxyanthraquinone [4, 5]. Alizarin and chrysazin are also formed depending on the properties of the aluminium oxide used [6]. 

There is a wide diversity of chemical structures of anthraquinone colorants. Many anthraquinone dyes are found in nature, perhaps the best known being alizarin, 1,2-dihydroxyanthraquinone, the principal constituent of madder (see Chapter 1). These natural anthraquinone dyes are no longer of significant commercial importance. Many of the current commercial range of synthetic anthraquinone dyes are simply substituted derivatives of the anthraquinone system. For example, a number of the most important red and blue disperse dyes for application to polyester fibres are simple non-ionic anthraquinone molecules, containing substituents such as amino, hydroxy and methoxy, and a number of sul-fonated derivatives are commonly used as acid dyes for wool. 

Quentel et al. [294] complexed copper with l,2-dihydroxyanthraquinone-3 sulfuric acid prior to determination by absorptive stripping voltammetry in amounts down to 0.3 nM in seawater. 

Anthracyclinones.1 Phthaloyl dichlorides undergo Friedel Crafts reactions with hydroquinones or the dimethyl ethers to give 1,4-dihydroxyanthraquinones in one step. 

Table 3.50 Structure and heat fastness of N-substituted amino-dihydroxyanthraquinone disperse dyes on polyester [190] ...

In a related series of 1,2,4-trisubstituted anthraquinone compounds, the effectiveness of various polar and nonpolar substituents to improve on the low heat fastness of 2-amino-1,4-dihydroxyanthraquinone (3.184 R = H) was examined (Table 3.50). Short-chain alkyl groups (methyl, ethyl) and even the pyranylmethyl ether are relatively ineffective but hydroxyalkyl, cyclohexyl, benzyl and morpholinylethyl groups show moderate increases. Further improvement is given by phenyl, pyridylmethyl and morpholinylpropyl. Outstandingly effective, however, are the benzothiazolyl, dodecylphenyl and fluoro-methylphenyl groupings. 

Although anthraquinone is the starting point for the preparation of many derivatives, involving substitution and replacement reactions, certain compounds are obtained directly by varying the components in the above synthesis. Thus, for example, replacement of benzene with methylbenzene (toluene) leads to the formation of 2-methylanthraquinone. A particularly important variation on the phthalic anhydride route is the synthesis of 1,4-dihydroxyanthraquinone (6.6 quinizarin) using 4-chlorophenol with sulphuric acid and boric acid as catalyst (Scheme 6.3). The absence of aluminium chloride permits hydrolysis of the chloro substituent to take place. 

The first group includes 1,2-dihydroxyanthraquinone, commonly known as alizarin, 1,4-dihydroxyanthraquinone (quinizarin), and 1,2,4-trihydroxyan-thraquinone (purpurin). Alizarin in particular has been known and appreciated for thousands of years in the form of its lake , i.e., the coordination complex of 1,2-hydroxyanthraquinone 88 with aluminum and calcium (Madder Lake, Turkey Red). 

The calcium lake of 1,2-dihydroxyanthraquinone is marketed as Pigment Red 83, 58000 1. It is produced commercially by treating a slightly basic alizarin solution with aqueous calcium chloride. 

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. 

Quinizarin.—1 4-dihydroxyanthraquinone is of no use as a dye it has been found, as a general rule, that only those polyhydroxyquinones of the anthracene and naphthalene series (naphthazarin) which have their adjacent OH-groups in positions adjoining the carbonyl group are capable of forming colour lakes. 

The fact that dihydroxyanthraquinones can be directly oxidised to higher phenols with fuming sulphuric acid is of technical importance. Alizarin and quinizarin yield in this way the same 1 2 5 8-tetra-hydroxyanthraquinone (alizarin bordeaux), which can be further oxidised to the important compound anthracene blue (1 2 4 5 6 8-hexa-hydroxyanthraquinone). This dye is obtained technically from 1 5-or 1 8-dinitroanthraquinone by means of a very interesting reaction,... 

Sometimes decomposition reactions can be avoided by carrying out diazotizations in concentrated sulfuric acid. By this method Law and coworkers45 obtained the 1,5-bisdiazonium salt (incorrectly called tetrazonium salt) of l,5-diamino-4,8-dihydroxyanthraquinone, which is deprotonated to 24. The structure was verified by cross-polarization magic angle spinning (CPMAS) 13C NMR spectroscopy. 

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