a group of dyes; aromatic compounds whose color results from the presence of nitro groups, NO2, and hydroxy and imino groups, OH and NHR (R is an alkyl or aryl group). They may also contain Cl, SO3H, and COOH substituents.
Nitro dyes containing imino groups are more stable. For example, 2K disperse fast yellow is of practical importance for dyeing a number of fibers:
It is produced by the reaction of 2,4-dinitrochlorobenzene with p-aminophenol.
Naphthol yellow (II) is used in a number of countries as a food dye. It is produced by sulfonation of α-naphthol, with subsequent nitration of the product.
The barium salt of naphthol yellow is used for dyeing paper pulp and in the production of colored pencils.
Nitro dyes (for example, picric acid) were among the first industrial dyes. They lost their practical importance as a result of their low stability.
REFERENCES
Kogan, I. M. Khimiia krasitelei, 3rd ed. Moscow, 1956.Chekalin, M. A., B. V. Passet, and B. A. Ioffe. Tekhnologiia organicheskikh krasitelei i promezhutochnykh produktov. Leningrad, 1972.
M. A. CHEKALIN
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