22 августа, 2015 
Pokraskin Once the second most important class of dyes, it also includes some of the oldest dyes; they have been found in the wrappings of mummies dating back over 4000 years. In contrast to the azo dyes, which have no natural counterparts, all the important natural red dyes were anthraquinones [1]. However, the importance of anthraquinone dyes has declined due to their low cost-effectiveness.
Anthraquinone dyes are based on 9,10-anthraquinone (1), which is essentially colorless. To produce commercially useful dyes, strongly electron donating groups such as amino or hydroxyl are introduced into one or more of the four a positions
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