Anthraquinone Acylaminoanthraquinones

Acylaminoanthraquinones. This dye class consists mainly of ben2oyl derivatives of aminoanthraquinones. Due to the relatively low molecular weight, this dye class is appHed in dyeing at low temperature. Yellow, orange, red, and even violet colors are covered by acylamino anthraquinones. 

On the basis of their chemical constitutions the anthraquinoid vat dyes may be classified in the following major groups acylaminoanthraquinones, anthraqui-noneazoles, anthrimides and other linked anthraquinones, anthrimidocarbazoles, phthaloylacridones, benzanthrone dyes, indanthrones, and other polycondensed ring systems. 

Acylaminoanthraquinones. Acylation of amino anthraquinones with benzoic acid or benzoyl chloride, for example, affords vat dyes with satisfactory affinity to cellulose fibers. The simplest dyes of this type, 1,4- and 1,5-dibenzoylaminoanthra-quinones, are no longer important. Bridging linkages, such as the dicarboxylic acids oxalic or phthalic acid, permit coupling of two anthraquinone units three amino anthraquinones may be combined by use of a triazine, such as cyanuric chloride. 

Acylation of 1-amino- or 1,5-diaminoanthraquinones yields yellow vat dyes and affords red to ruby colored dyes when 1,4-diaminoanthraquinones are used. Use of 4,8-diamino-l,5-dihydroxy-anthraquinones gives violet to blue dyes. The relatively low lightfastness of the yellow acylaminoanthraquinones may be improved greatly by using azodiphenyl-4,4 -dicarboxv 1 ic acid. Acylaminoanthraquinones are relatively sensitive to atmospheric conditions. 

Nitration of anthraquinones has considerable industrial importance. Examples of compounds that may be nitrated are anthraquinone and the halo-, hydroxy-, amino-, and acylaminoanthraquinones. As a rule the nitro group attacks at the a-position choice of reaction conditions frequently permits mono- or dinitration. 

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