GB659684A - Improvements in the production of 1-amino-2-sulpho-4-halogen-anthraquinones - Google Patents

Abstract

1 - Amino - 2 - sulpho - 4 - bromo- or 4-chloroanthraquinone is made by subjecting an aqueous solution of 1-amino-2-sulpho-anthraquinone to the action of a current of inert gas, e.g. air, carrying bromine or chlorine in gaseous form. Reaction is effected at about 0 DEG C. and the inert gas is given its bromine content by passing at a temperature of about 130-180 DEG C. through liquid bromine at preferably 10-25 DEG C. Advantageously inorganic salts such as sodium chloride or sulphate or potassium chloride should be present in such concentration that the product is precipitated from solution as soon as formed, c.f. Specification 598,797. For the above bromination reaction the concentration of sodium chloride quoted is 3-4.5 per cent by weight. The concentration of 1-amino-2-sulpho-anthraquinone in the aqueous salt solution is preferably from 2.5-4 per cent, advantageously 3-3.5 per cent, by weight. Bromine concentration is preferably maintained at 0.05-0.07 per cent by weight during bromination, reaction being stopped when it rises to about 0.09-0.1 per cent. In an example, bromine in dry air is passed for 6-9 hours through an aqueous sodium chloride solution of 1-amino-2-sulpho-anthraquinone at about 0 DEG C. and when reaction ceases the reaction mixture is heated to about 90 DEG C. to dissolve the precipitated product, more sodium chloride is added and the product obtained on gentle cooling is filtered off and recrystallized from hot water, the filtrate being recycled for use as bromination reaction medium.