C(O)(=O)C1C(=CC=CC=1)C(O)=O.ClCl.[OH-].[Na+].[Cl:17][C:18]1[CH:19]=[C:20]([C:28]([OH:30])=[O:29])[C:21](=[CH:25][C:26]=1Cl)[C:22]([OH:24])=[O:23].ClC1C(Cl)=CC=C(C(O)=O)C=1C(O)=O.ClC1C=CC(Cl)=C(C(O)=O)C=1C(O)=O.ClC1C=C(C(O)=O)C(C(O)=O)=C(Cl)C=1Cl>O>[Cl:17][C:18]1[CH:19]=[C:20]([C:28]([OH:30])=[O:29])[C:21](=[CH:25][CH:26]=1)[C:22]([OH:24])=[O:23]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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