16,17- violanthrone

S. violaceus Viola method Violanthrone dyes Violan thrones Violet acid [578-85-8]... 

Diben2anthronyl [116-90-5] (72) is a precursor of violanthrone dyes and is prepared from an alcohoHc alkaU melt of ben2anthrone. 

Benzanthrone Dyes. Vat dyes derived from benzanthrone may be divided into two groups violanthrones and isoviolanthrones, dyes that have the perylene ring in their molecular stmcture and benzanthrone pyrazolanthrones and benzanthrone acridones, the peri ring closure products of 3-anthra quin onyl amino-ben zanthrone. 

Violanthrone andIsoviolanthrone Dyes. Violanthrone dyes cover a wide range of shades from reddish blue to green and grey. Examples of dyes that have industrial importance appear in Table 5. 

Figure 12.1.9 The molecular structure of 16,l7-(l,2-ethylenedioxy)violanthrone with R... R = -OCH2CH2O- and 16,17-dihexyloxyviolanthrone with each R = -OCgH. ...

When dibenzal diperoxide 3 was added, at 200°, to a solution of di-benzanthrone a red chemiluminescence was observed67) this is also seen in the reaction of violanthrone (dibenzanthrone) with alkaline hydrogen peroxide/chlorine. 

Owing to experimental difficulties, knowledge of aggregation effects in alkaline dithionite solutions of leuco vat dyes is sporadic [20,21]. Investigations based on absorption spectra have shown that, depending on concentration and temperature, planar polycyclic molecules such as the violanthrone derivatives Cl Vat Blues 19, 20 and 22 and the perylene tetracarboxydiimide derivatives Cl Vat Reds 23 and 32 are mainly present as monomers or dimers in leuco vat solutions. Violanthrones that do not have a coplanar structure because of the presence of... 

In 1904 Bally obtained a bluish violet solid by alkali fusion of benzanthrone at approximately 220 °C. Two isomeric compounds were isolated by vatting the reaction mixture and filtering off a sparingly soluble sodium salt. Oxidation of the filtrate gave a blue vat dye, violanthrone (6.75 Cl Vat Blue 20), as the main component. The less soluble residue similarly afforded a violet product, isoviolanthrone (6.76 Cl Vat Violet 10). The formation of isoviolanthrone can be suppressed by carrying out the fusion in a solvent such as naphthalene or a polyethylene glycol in the presence of sodium acetate and sodium nitrite. Dyes of this type are often referred to as dibenzanthrones. 

It was established in 1929 by Liittringhaus and Neresheimer that 4,4,-bibenzanthronyl (6.77) is an intermediate in the formation of violanthrone. Thus, compound 6.77 results when an Ullmann reaction is carried out on 4-chlorobenzanthrone the same product is obtained when benzanthrone reacts under relatively mild conditions (approximately 110 °C) with a mixture of potassium hydroxide and potassium acetate in 2-methylpropan-l-ol (isobutanol). Alkali fusion at a higher temperature then converts 4,4,-bibenzanthronyl into violanthrone. Use of aluminium chloride also leads to ring closure (Scholl reaction). 

Violanthrone and isoviolanthrone are effectively cis and turns isomers. The important cis compound absorbs more intensely and at a longer wavelength than the turns isomer (Table... 

A redder and brighter shade is obtained with isoviolanthrone. Its halogenation products are marketed as brilliant violet dyes. Related to violanthrone is the alkaline ring-closure product of 3-pyrazolanthronylbenzanthrone, which is used as a navy blue vat dye. 

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