Sulphurised Vat Dyes - 2
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This group constitutes complex sulphur linkages having characteristic grouping by the virtue of which, the dyes can be vatted, as these groupings have quinonoid type of structurers. The dye is applied on cotton as a vat dye and regenerated on fibre by oxidation. Hydron Blue R (64) is an important example of this class. It is prepared by the thionation of carbazole derivative (692). Unsubstituted carbazole at —20 to —250C and the productr obtained is reduced to get the carbazole derivative (692) which is refluxed for 24 hours with sodium polysulphide and sodium nitrite in butanol and the solvent butanol is distilled off to give the dye (64).
