Pyridine → 1,4-Diamino-9,10-dihydro-9,10-dioxoanthracene-2-sulphonic acid

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

60 parts of 1,4-diaminoanthraquinone are added to 228 parts of 25% oleum over one hour and then 20 parts of pyridine are added. The temperature of the reaction mixture is 70°-80° C. and is further raised to 120° C. The reaction mixture is stirred at this temperature for 3 hours, then cooled to 70°-80° C., and 220 parts of water are slowly added dropwise. The resultant thick suspension is filtered at room temperature and the filter cake is washed with 100 parts of 50% sulfuric acid and subsequently dispersed in water. The pH of the aqueous suspension is then adjusted to 7.5 with 35% sodium hydroxide solution, whereupon the 1,4-diaminoanthraquinone-2sulfonic acid goes into solution. The solution is then heated to 85°-90° C. and 40 parts of magnesium sulfate are added. Upon cooling the reaction solution, the 1,4-diaminoanthraquinone-2-sulfonic acid crystallises in the form of the magnesium salt, which is isolated by filtration, washed with a 5% solution of magnesium sulfate and dried, affording 72.4 parts of the magnesium salt of 1,4-diaminoanthraquinone-2-sulfonic acid, corresponding to a yield of 85%. According to chromatographic analysis, the product is homogeneous with a trace of starting material. The Rf value is 0.57, which confirms that this product is identical with that obtained in Example 1.

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