Sulfuric Acid → Sulfuric Acid

Participants

Reaction Conditions

Reaction Steps

80 parts of leuco-1,4-diaminoanthraquinone are added to 270 parts of 100% sulfuric acid over 30 minutes, the temperature rising to 65°-70° C. The solution is heated to 110° C. and then 90 parts of 66% oleum are added initially over 1 hour, followed by the dropwise addition of a further 80 parts of 66% oleum over the next 3 hours. The reaction mixture is then stirred for a further 4 hours at 110° C., cooled to room temperature and poured onto 255 parts of ice. The resultant brown suspension is filtered at room temperature, affording crude 1,4-diaminoanthraquinone-2-sulfonic acid which still contains sulfuric acid and is of sufficient purity that it can be used in this form direct for the dye synthesis, especially if the subsequent synthesis is carried out in sulfuric acid in any case.

Provenance & Evidence