3,4,5,6-Tetrafluorophthalic acid → 2,3,4,5-Tetrafluorobenzoic acid

Participants

Reaction Conditions

Reaction Steps

In a flask of an inner volume of 1 liter, 200 g (1.0 mole) of 3,4,5,6-tetrafluorophthalonitrile, 459 g of sulfuric acid, and 391 g of water were placed and heated and stirred for reaction under reflux for 17 hours. After completion of the reaction, the reactant was cooled. The precipitate of 3,4,5,6-tetrafluorophthalic acid consequently formed was separated by filtration. The cake, on analysis, was found to contain 5.0% by weight of sulfuric acid, 2.0% by weight of ammonium sulfate, and 7.2% by weight of water in addition to 3,4,5,6-tetrafluorophthalic acid. In an autoclave having an inner volume of 1 liter, 175 g (150 g as tetrafluorophthalic acid) of a total of 263 g of the cake, 14.0 (0.189 mole) of calcium hydroxide, and 500 g of water were placed and heated and stirred for decarboxylation at 160 ° C. for 18 hours [pH 1.90 at 70° C. at the time of charging]. The reaction mixture was then treated thereafter by following the procedure of Example 1, to produce white 2,3,4,5-tetrafluorobenzoic acid. By the same calculation as in Example 1, this example was found to have produced 2,3,4,5-tetrafluorobenzoic acid in a yield of 96.4 mole % based on 3,4,5,6-tetrafluorophthalic acid.

Provenance & Evidence