Dyes, anthraquinone preparation

Various more complex dyes of industrial significance contain more than one carbazole system. For example, Cl Vat Orange 11 (6.86) contains two carbazole components and a central unit derived from 1,5-diaminoanthraquinone. This dye is prepared by carbazolisation of the trianthrimide produced when two moles of 1-chloroanthraquinone react with one mole of 1,5-diaminoanthraquinone. The equivalent isomeric dye obtained from 1,4-diamino-anthraquinone is reddish brown (6.87 Cl Vat Brown 1). The interesting, symmetrically-substituted tetracarbazole dye Cl Vat Green 8 (6.88) was first synthesised in 1911 by Hepp from 1,4,5,8-tetrachloroanthraquinone. Not surprisingly, the product (C70H28N4Oio relative molecular mass 1084) is of very low solubility. The structure was confirmed in 1957 by Jayaraman, who found no evidence of uncyclised anthrimides in the UV spectrum of the dye solution in concentrated sulphuric acid [32]. 

Since, as the equation shows, this substance is converted by-concentrated sulphuric acid with loss of water into anthraquinone, a very important route to a much-studied group is opened up. Thus /S-methylanthraquinone, which serves as an intermediate for valuable vat dyes, is prepared technically in this way from phthalic anhydride and toluene. 

Pigment Red 177 [4051-63-2] has the chemical structure of 4,4 -diaminol,l -dianthraquinonyl and is prepared by intermolecular copper-catalyzed debromination of l-amino-4-bromoanthraquinone-2-sulfonic acid followed by desulfonation. It is the only known pigment with unsubstituted amino groups which are involved in both intra- and intermolecular hydrogen bonding (19). The bluish red pigment is used in plastics, industrial and automotive paints, and specialized inks (see Dyes, ANTHRAQUINONE). 

Anthraquinone dyes are prepared by the stepwise introduction of substituents on to the performed anthraquinone skeleton or ring closure of appropriately substituted precursors. 

Anthraquinone dyes are prepared by the stepwise introduction of substituents onto the preformed anthraquinone skeleton (1) or ring closure of appropriately substituted precursors. The degree of freedom for producing a variety of different structures is restricted, and the availability of only eight substitution centers imposes a further restriction on synthetic flexibility. Therefore, there is significantly less synthetic versatility than in the case of azo dyes, and consequently less variety this is a drawback of anthraquinone dyes. 

Some 80 % of anthraquinone dyes are prepared via the anthraquinone sulfonic acids. In producing certain dyes, the sulfonic acid group is replaced by a hydroxyl group using high pressure fusion with lime [31.28]. 

Dyes, Dye Intermediates, and Naphthalene. Several thousand different synthetic dyes are known, having a total worldwide consumption of 298 million kg/yr (see Dyes AND dye intermediates). Many dyes contain some form of sulfonate as —SO H, —SO Na, or —SO2NH2. Acid dyes, solvent dyes, basic dyes, disperse dyes, fiber-reactive dyes, and vat dyes can have one or more sulfonic acid groups incorporated into their molecular stmcture. The raw materials used for the manufacture of dyes are mainly aromatic hydrocarbons (67—74) and include ben2ene, toluene, naphthalene, anthracene, pyrene, phenol (qv), pyridine, and carba2ole. Anthraquinone sulfonic acid is an important dye intermediate and is prepared by sulfonation of anthraquinone using sulfur trioxide and sulfuric acid. 

Anthraquinone dyes are derived from several key compounds called dye intermediates, and the methods for preparing these key intermediates can be divided into two types (/) introduction of substituent(s) onto the anthraquinone nucleus, and (2) synthesis of an anthraquinone nucleus having the desired substituents, starting from benzene or naphthalene derivatives (nucleus synthesis). The principal reactions ate nitration and sulfonation, which are very important ia preparing a-substituted anthraquiaones by electrophilic substitution. Nucleus synthesis is important for the production of P-substituted anthraquiaones such as 2-methylanthraquiQone and 2-chloroanthraquiaone. Friedel-Crafts acylation usiag aluminum chloride is appHed for this purpose. Synthesis of quinizatia (1,4-dihydroxyanthraquiQone) is also important. 

Efforts to raise the alpha-selectivity have been made. Thus nitration of anthraquinone using nitrogen dioxide and ozone has been reported (17). l-Amino-4-bromoanthraquinone-2-sulfonic acid (bromamine acid) [116-81 -4] (8) is the most important intermediate for manufacturing reactive and acid dyes. Bromamine acid is manufactured from l-aminoanthraquinone-2-sulfonic acid [83-62-5] (19) by bromination in aqueous medium (18—20), or in concentrated sulfuric acid (21). l-Aminoanthraquinone-2-sulfonic acid is prepared from l-aminoanthraquinone by sulfonation in an inert, high boiling point organic solvent (22), or in oleum with sodium sulfate (23). 

Chloroanthraquinone [82-44-0] (41) is an intermediate for manufacturing vat dyes such as Cl Vat Brown 1. 1-Chloroanthraquinone is prepared by chlorination of anthraquinone-l-sulfonic acid with sodium chlorate in hydrochloric acid at elevated temperature (61). An alternative route from 1-nitroanthraquinone (18) using elemental chlorine at high temperature has been reported (62). 

Acid—mordant dyes have characteristics similar to those of acid dyes which have a relatively low molecular weight, anionic substituents, and an affinity to polyamide fibers and mordant dyes. In general, brilliant shades caimot be obtained by acid—mordant dyes because they are used as their chromium mordant by treatment with dichromate in the course of the dyeing procedure. However, because of their excellent fastness for light and wet treatment, they are predominandy used to dye wool in heavy shades (navy blue, brown, and black). In terms of chemical constitution, most of the acid—mordant dyes are azo dyes some are triphenyhnethane dyes and very few anthraquinone dyes are used in this area. Cl Mordant Black 13 [1324-21 -6] (183) (Cl 63615) is one of the few examples of currentiy produced anthraquinone acid—mordant dyes. It is prepared by condensation of purpurin with aniline in the presence of boric acid, followed by sulfonation and finally by conversion to the sodium salt (146,147). 

Water-soluble polymeric dyes have been prepared from water-insoluble chromophores, viz., anthraquinone derivatives. Unreacted chromophore and its simple derivatives, which are all water-insoluble, remain in solution due to solubilization by the polymeric dye. A method has been developed to separate and quantitate the polymeric dye and these hydrophobic impurities using Sephadex column packing. The solvent developed has the property of debinding the impiirities from the polymer, and further allows a separation of the imp irities into discrete species. This latter separation is based on the functional groups on the impurity molecules, having a different interaction with the Sephadex surface in the presence of this solvent. The polymer elutes at the void volume... 

In an interesting study, phthalocyanine complexes containing four anthraquinone nuclei (5.34) were synthesised and evaluated as potential vat dyes and pigments [18]. Anthraquinone-1,2-dicarbonitrile or the corresponding dicarboxylic anhydride was reacted with a transition-metal salt, namely vanadium, chromium, iron, cobalt, nickel, copper, tin, platinum or lead (Scheme 5.6). Substituted analogues were also prepared from amino, chloro or nitro derivatives of anthraquinone-l,2-dicarboxylic anhydride. 

Benzanthrone (6.73) is the source of various commercially important violet, blue and green vat dyes. This tetracyclic system can be prepared from a mixture of anthraquinone and propane-1,2,3-triol (glycerol) by heating with iron powder in concentrated sulphuric acid. The reaction involves reduction of anthraquinone to anthrone (6.74) followed by condensation (Scheme 6.14) with propenal (acrolein), the latter compound being generated... 

Two different chemical classes contribute to this sector. Initially it was entirely dominated by anthraquinone dyes typified by structure 7.102. The dye bases for attachment of haloheterocyclic (Z) systems are prepared by condensing bromamine acid (7.103) with various phenylenediamines. The outstandingly successful Cl Reactive Blue 19 (7.3 7) is the... 

Uses Dyes starting material for the preparation of alizarin, phenanthrene, carbazole, 9,10-anthraquinone, 9,10-dihydroanthracene, and insecticides in calico printing as component of smoke screens scintillation counter crystals organic semiconductor research wood preservative. 

The anthraquinone vat dyes provide, in certain instances, the ultimate in fastness properties although the shades are often rather dull. The products are, however, frequently difficult to prepare commercially, requiring multistage small-batch operations and are thus less economically viable than related dye classes. Thus, they are used almost exclusively in high quality outlets of long life expectancy. An example of historic interest is the dye formed by condensation of two molecules of 1-aminoanthraquinone and one of cyanuric chloride (9) which was discovered in 1921 (Cl Vat Orange 18). The significance of the reactive... 

Other five-membered heterocycles such as thiophenes, thiazoles and oxazoles have been successfully annellated in the anthraquinone series. For example, the yellow dye (12) may be prepared from 2,6-diaminoanthraquinone by condensation with benzotrichloride and sulfur. Similarly, the six-membered heterocycles acridines, quinoneazines, pyrazines, acridones and pyrimidines are frequently incorporated (B-52MI11201). In fact, the best known of the anthraquinone vat dyes are indanthrone (13) and flavanthrone (14). The former anthraquinoneazine, a beautiful blue, which was the first such structure to be manufactured on a large scale, may be prepared by alkali fusion of 2-aminoanthraquinone at 220 °C (27MI11200). Treatment of 2-aminoanthraquinone in nitrobenzene with antimony pentachloride yields the yellow flavanthrone (14), the structure being confirmed by Scholl (07CB1691). Both indanthrone and flavanthrone and their derivatives have attracted considerable commercial attention. 

I -Methylaminoanthraquinonc is an important intermediate for manufacturing solvent dyes and acid dyes, and is prepared from anthraquinone-1-sullonic acid by replacing the SOtH group with methylamine. 

Dichloroanlhraquinonc is an important intermediate for vat dyes and disperse blue dyes. 1.5-Dichloroanlhraquinone is prepared by the reaction of anthraquinone- 1,5-disuifonic acid with NaCIO in hot hydrochloric acid solution. 

Diaminoamhraquinone is prepared from 1.5-dmitroanlhraquinone by ammonnlysis, by catalytic hydrogenation, or by reduction with sodium sulfide. It is also prepared From anthraquinone-],5-disulfonic acid by ammonolysis. 1.5-Diaminoanlhraquinone is an important intermediate lor manufacturing vat dyes. 

Bemanthrone and Related Compounds. Benzanthrune is prepared by the reaction of anthraquinone with glycerol, sulfuric acid, and a reducing agent such as iron. Benzanchrone is an important intermediate for manufacturing vat dyes. 

The production of anthraquinone dyes generally proceeds from a few key products generated by electrophilic substitution of unsubstituted anthraquinone or by synthesis of the nucleus. The major methods employed to prepare anthraquinone derivatives substituted in the a-position are sulfonation and nitration. Preparation of b-substituted anthraquinones and of quinizarin (1,4-dihydroxyan-thraquinone) generally is accomplished by synthesis of the nucleus starting from phthalic anhydride and a benzene derivative. 

From about 1930 onwards, developments in the field of naphthoquinone dyes concentrated on the use of naphthazarin and intermediates for the preparation of violet, blue, and green acid and disperse dyes [1]. More recently there has been interest in the synthesis and color and constitution properties of simple colored naphthoquinones, stimulated by the fact that such dyes have similar tinctorial properties to the anthraquinones but a smaller molecular size. The naphthoquinones provide a useful alternative to the anthraquinones for certain specialized applications, e g., as pleochroic dyes with improved solubility for liquid-crystal displays. As a result, research interest in these chromogens remains unabated, even though they have failed to make any major impact as textile dyes [2-8],... 

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