Methylated Derivatives of 4,8-Diamino-1,5-dihydroxyanthraquinone and 4,5-Diamino-1,6-dihydroxyanthraquinone – Blue Dyes for Synthetic-polymer Fibres

The synthesis of N-methylated derivatives of 4,5-diamino-1,6-dihydroxyanthraquinone (DACZ) and of 4,8-diamino-1,5-dihydroxyanthraquinone (DAAR) is described. All possible N-methyl derivative of DAAR were obtained, but the tetramethylated derivative of DACZ could not be isolated. Attempts to synthesise an asymmetrical N,N-dimethyl derivative of DACZ were also unsuccessful, only an N,O-dimethylated derivative being obtained. The colour of the dyes is discussed in relation to the degree of methylation, and solvent effects on absorption maxima are also reported