METHOD OF SELECTING AND CLEANING 4-CHLOROPHTHALIC ACID OF MONOMERIC CLEANLINESS DEGREE Russian patent published in 2018 - IPC C07C51/02 C07C51/48 C07C63/72 

FIELD: chemistry.

SUBSTANCE: aqueous solution of phthalic anhydride chlorination products of sodium hypochlorite - a mixture of sodium salts of phthalic acids, is treated with concentrated hydrochloric acid strictly to pH 6.8-6.9, then the mixture is extracted with ethyl acetate, the aqueous and ethyl acetate layers are separated, 4-chlorophthalic acid with a purity of up to 99%. The aqueous layer containing the original phthalic acid is combined with the chlorination checker after the extraction, and the chlorination operation is repeated. The yield of the desired 4-chlorophthalic acid reaches 87%.

EFFECT: increasing the yield.

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