L-Amino-2,4-dibromoanthraquinone

Contamination by water-insoluble reaction by-products such as l-amino-2,4-dibromoanthraquinone affects the quaUty of dyestuff signiftcandy. Therefore, several methods for purification have been reported. Examples are extraction of impurities with organic solvent (18), or precipitation of bromamine acid from concentrated (60—85%) sulfuric acid (26). 

Use of the intermediates l-amino-2,4 dibromoanthraquinone and l-aminO 4 bromO 2 methylanthraquinone leads to similar dyes, exemplified by Cl Acid Blue 78 (6.34 X = Br) and Cl Acid Blue 47 (6.34 X = CH3) respectively in the production of these two dyes, sulphonation is the final step. 

Dyes for cellulose acetate are relatively simple molecules, typified by Cl Disperse Red 15 (6.39 X = OH), Cl Disperse Violet 4 (6.39 X = NHCH3) and Cl Disperse Blue 3 (6.40), the last-named being manufactured from leucoquinizarin and the appropriate amines. The unsymmetrically substituted product inevitably contains significant amounts of the related symmetrical compounds. The widely used Cl Disperse Blue 3 is known to cause skin sensitisation when on nylon [17] and can also provoke an allergic reaction [18]. Bright red 2-alkoxy-l-amino-4-hydroxyanthraquinones, such as Cl Disperse Red 4 (6.41), can be obtained from l-amino-2,4-dibromoanthraquinone by hydrolysis to give l-amino-2-bromo-4-hydroxyanthraquinone (Cl Disperse Violet 17), which is then condensed with the appropriate alcohol. 

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