Phthalic Acid → 4-Chlorophthalic acid

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Reaktionsschritte

The chlorination of the phthalic acid is effected in analogy with known methods in water at 45° to 50° by admitting chlorine gas with the pH value being kept at approximately 5 by the addition of aqueous sodium hydroxide. After approximately 10 hours reacting, a mixture containing approximately 63% 4,5-dichlorophthalic acid, 17% 3,4-dichlorophthalic acid, 9% 3,6-dichlorophthalic acid, 6% trichlorophthalic acid and 4% 4-chlorophthalic acid (chromatographic analysis) is obtained. The mixture is heated under low vacuum to approximately 200° to yield the corresponding chlorophthalic acid anhydride. The product is employed as such for the reaction with the 1,8-diaminonaphthalene.

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