Anthraquinone and anthrone series

Summary

Hydrolysis of Indanthrene Yellow 4GK gives 8-aminopyrimidanthrone (II) and 2∶5-dichlorobenzoic acid; the dye is therefore the 8-(2′∶5′-dichloro)-benzamidopyrimidanthrone (I). Indanthrene Yellow 7GK is thep-chlorobenzoyl derivative (V) of 6-aminopyrimidanthrone (IV). The ability of a pyrimidanthrone derivative to function as a vat dye, although it possesses only one carbonyl group, results from an increase in the acid strength of the leuco compound by the resonance stabilization of the anion as indicated in structures (III A) and (III B).

Unlike many yellow and orange anthraquinonoid vat dyes, Indanthrene Yellow 4GK and 7GK do not accelerate the photochemical oxidation of cellulose. Differences in the behaviour of anthraquinone derivatives and of pyrimidanthrone derivatives in the action of light on cellulose are explained on the basis of the relative stability of their semiquinone ions.