Vat Green

Although the colors of the polycycHc aromatic carbonyl dyes cover the entire shade gamut, only the blue dyes and the tertiary shade dyes, namely, browns, greens, and blacks, are important commercially. Typical dyes are the blue indanthrone [81-77-6] (40), the brown Cl Vat Brown 3 [131-92-0] (Cl 69012), (41), the black Cl Vat Black 27 [2379-81-9] (42), and the green Cl Vat Green 1 [128-58-5] (Cl 59825) (43), probably the most famous of all the polycycHc aromatic carbonyl dyes. 

Cl Vat Green 3 is prepared from 3-bromoben2anthrone (73) and 1-aminoanthraquinone (17) as foUows ... 

The deeper shades are obtained by addition of other heterocycHc systems, such as quina2oline, to the molecular stmcture. Cl Vat Green 12... 

Table 12.32 Effect of particle size on rate of reduction of Cl Vat Green 1 at 20 °C [221]...

The times of half-reduction of five typical vat dyes are listed in Table 3.3. Most of the commercially important products give values within the range 25-500 seconds. Few dyes are as slow to reduce as Cl Vat Red 1 and even fewer are reduced as quickly as flavanthrone. In fact, when these times were measured the average particle size of the sample of flavanthrone under test was greater than that of the Cl Vat Green 1 sample, which was reduced at least ten times more slowly [26]. 

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]. 

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