1- Hydroxyanthraquinone

Prepared by condensing p-chlorophenol with phlhalic anhydride in sulphuric acid solution in the presence of boric acid. The chlorine atom is replaced by hydroxyl during the condensation. It can also be prepared by oxidation of anthraquinone or 1-hydroxyanthraquinone by means of sulphuric acid in the presence of mercury(ll) sulphate and boric acid. 

Marzocchi M P, Mantini A R, Casu M and Smulevich G 1997 Intramolecular hydrogen bonding and excited state proton transfer in hydroxyanthraquinones as studied by electronic spectra, resonance Raman scattering, and transform analysis J. Chem. Phys. 108 1-16... 

Included in this grouping are D C Green No. 5 (13), a water-soluble sulfonate, D C Green No. 6 (14), an unsulfonated water-insoluble compound, and D C Violet No. 2 (29), a water-insoluble hydroxyanthraquinone. Anthraquinone color additives, in general, are light stable and have good physical and chemical properties for use in cosmetics (see Dyes, ANTHRAQUINONE). 

Cochineal Extract. Cochineal extract (Cl Natural Red 4, Cl No. 75470 EEC No. E 120) is the concentrated solution obtained after removing the alcohol from an aqueous-alcohoHc extract of cochineal, which is the dried bodies of the female insect Coccus cacti Dactylopius coccus costd) a variety of field louse. The coloring principle of the extract is beHeved to be carminic acid [1260-17-9] (40), an hydroxyanthraquinone linked to a glucose unit, comprising approximately 10% of cochineal and 2—4% of its extract. 

Subsequendy, H. Caro and W. H. Perkin independendy developed the commercial manufacturing process of alizarin from anthraquinone (qv) through anthraquinone-2-sulfonic acid. Taking advantage of these inventions, many manufacturers came to produce various kinds of hydroxyanthraquinones, which were used as mordant dyes for dyeing cotton and wool. 

Efforts have also been made to overcome compHcated processes. Methods to reduce the number of steps or to use new starting materials have been studied extensively. l-Amino-2-chloro-4-hydroxyanthraquinone (the intermediate for disperse red dyes) conventionally requires four steps from anthraquinone and four separation (filtration and drying) operations. In recent years an improved process has been proposed that involves three reactions and only two separation operations starting from chloroben2ene (Fig. 2). 

Fig. 2. Manufacturing processes for the dye intermediate l-amino-2-chloro-4-hydroxyanthraquinone [2478-67-3].

The main by-products of the Ullmaim condensation are l-aniinoanthraquinone-2-sulfonic acid and l-amino-4-hydroxyanthraquinone-2-sulfonic acid. The choice of copper catalyst affects the selectivity of these by-products. Generally, metal copper powder or copper(I) salt catalyst has a greater reactivity than copper(Il) salts. However, they are likely to yield the reduced product (l-aniinoanthraquinone-2-sulfonic acid). The reaction mechanism has not been estabUshed. It is very difficult to clarify which oxidation state of copper functions as catalyst, since this reaction involves fast redox equiUbria where anthraquinone derivatives and copper compounds are concerned. Some evidence indicates that the catalyst is probably a copper(I) compound (28,29). 

Furthermore, a method using formaldehyde in the second step (hydrolysis) instead of boric acid has been reported recendy (33). l-Amino-4-hydtoxyanditaquinone [116-85-8] (26) is also brominated to form l-amino-2-bromo-4-hydroxyanthraquinone [116-82-5]. Bromination is carried out in an inert organic solvent such as nitroben2ene (34). 

Fig. 5. Synthesis of l-amino-4-hydroxyanthraquinones with alkoxy substituents in the 2-position. See Table 4.

Table 4. Disperse Red Dyes, 2-Substituted l-Amino-4-hydroxyanthraquinones...

A Substituted-l-Amino-4-hydroxyanthraquinones. These dyes show good affinity and hghtfastness and give violet to blue shades. However, the sublimation fastness is in general not satisfactory. An example is Cl Disperse Blue 72 [81-48-1] (117) (Cl 60725), prepared from leucoquinizarin and -toluidine. 

Alkylamines react with leucoquinizarin in a stepwise manner to give l-alh anaino-4-hydroxyanthraquinone, and 1,4-diaLkylamino derivatives after air oxidation. Aromatic amines react similarly in the presence of boric acid as a catalyst. The complex formed (129) causes the less nucleophilic aromatic amines to attack at the 1-, and 4-positions. 

Cl Vat Red 10 is prepared by condensation of l-nitroanthraquinone-2-carboxyhc acid chloride with 2-amino-3-hydroxyanthraquinone followed by ring closure in sulfuric acid and subsequent replacement of the nitro group with aqueous ammonia. 

Hypericin which is a hydroxyanthraquinone and the antibiotic nystatin also yield fluorescent zones. A higher fluorescence intensity is frequently obtained by heating to 88° C for 2 — 5 min instead of simply allowing to dry at room temperature. 

S-Hydroperoxylanostenyl acetate 62 Hydroquinone see Dihydroxybenzene n-Hydroxy acids 71 Hydroxyanthraquinones 148,288... 

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. 

C-NMR. The structures of the leuco derivatives of l,4-bis(butylamino)-anthraquinone (14) and l-butylamino-4-hydroxyanthraquinone (15) have been shown to be l,4-bis(butylamino)-2,3-dihydroanthracene-9,10-dione (16a) and l-butylamino-10-hydroxy-2,3-dihydroanthracene-4,9-dione (17a), respectively. On the other hand, leuco-1,4-dimethoxyanthraquinone has been assigned the structure, 1,4-dimethoxy-9,10-dihydroxyanthracene (18). 

It is well known that quinizarin (22) is alkylaminated in air to give a mixture of l-alkylamino-4-hydroxyanthraquinone (23), l,4-bis(alkylamino)-anthraquinone (24), and 2-alkylaminoquinizarin (25) (Scheme 7). The reaction conditions affect the ratio of these products. In a nitrogen atmosphere, or in the presence of sodium dithionite as reducing agent, the main amination product is 24. The solvent effects of the reaction of leuco... 

Dyes for cellulose acetate are relatively simple molecules, typified by Cl Disperse Red 15 (6.39 X = OH), Cl Disperse Violet 4 (6.39 X = NHCH3) and Cl Disperse Blue 3 (6.40), the last-named being manufactured from leucoquinizarin and the appropriate amines. The unsymmetrically substituted product inevitably contains significant amounts of the related symmetrical compounds. The widely used Cl Disperse Blue 3 is known to cause skin sensitisation when on nylon [17] and can also provoke an allergic reaction [18]. Bright red 2-alkoxy-l-amino-4-hydroxyanthraquinones, such as Cl Disperse Red 4 (6.41), can be obtained from l-amino-2,4-dibromoanthraquinone by hydrolysis to give l-amino-2-bromo-4-hydroxyanthraquinone (Cl Disperse Violet 17), which is then condensed with the appropriate alcohol. 

Monoarylation of l-amino-4-hydroxyanthraquinone (6.39 X = OH) results in violet dyes such as Cl Disperse Violet 27 (6.44 R = H) and the bluish violet Cl Disperse Blue 72 (6.44 R = CH3) the latter dye is also important as Cl Solvent Violet 13. Chlorination of 1,4-diaminoanthraquinone with sulphuryl chloride gives the 2,3-dichloro derivative (Cl Disperse Violet 28), which on condensation with phenol yields Cl Disperse Violet 26 (6.45). Monoaryl or dialkyl derivatives of 1,4-diaminoanthraquinone (6.19 Cl Disperse Violet 1) are blue. Typical examples include Cl Disperse Blue 19 (6.46) and Cl Disperse Blue 23 (6.47). 

Heterocyclic ring systems are also used to connect two anthraquinone groups. Typical examples include Cl Vat Red 10 (6.106), which is an oxazole derivative obtained from 2-amino-3-hydroxyanthraquinone and the appropriate acyl chloride, the similar thiazole derivative Cl Vat Blue 31 (6.107) and the oxadiazole derivative Cl Vat Blue 64 (6.108). 

This chapter classifies polycyclic pigments by chemical constitution. The resulting classes include aminoanthraquinones, hydroxyanthraquinones, heterocyclic and polycarbocyclic anthraquinone pigments. 

---