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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. |
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With calcium hydroxide; ammonium sulfate; sulfuric acid; In water; |
EXAMPLE 6 Decarboxylation of 3,4,5,6-tetrafluorophthalic acid was carried out by following the procedure of Example 1, except that 238 g (1.00 mole) of 3,4,5,6-tetrafluorophthalic acid, 13.8 g (0.140 mole) of sulfuric acid, 5.5 g (0.042 mole) of ammonium sulfate, 22.2 g (0.30 mole) of calcium hydroxide, and 480 g of water were used [pH 1.89 at 70 C. at the time of charging]. This example was found to have produced 2,3,4,5-tetrafluorobenzoic acid in a yield of 95.4 mole %. |
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With calcium hydroxide; In water; |
EXAMPLE 7 Decarboxylation of 3,4,5,6-tetrafluorophthalic acid was carried out by following the procedure of Example 1, except that 238 g of 3,4,5,6-tetrafluorophthalic acid, 11.1 g (0.15 mole) of calcium hydroxide, and 480 g of water were used [pH 1.52 at 30 C. at the time of charging]. This example was found to have produced 2,3,4,5-tetrafluorobenzoic acid in a yield of 86.5 mole %. |
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In a four-neck flask equipped with a stirrer, thermometer, and condenser, add 24g3,4,5,6-tetrafluorophthalic acid,200g drinking water, 25g calcium chloride, warmed to 50 ~ 55 C,The whole solid was dissolved and stirred at this temperature for 3 hours. Then slowly add 20% ammonia solution.To pH gradually approaching neutrality, when the pH value reaches 6.0 to 7.0, stop dropping, at 50After stirring at -55C for 30 minutes, the retest pH was unchanged and the reaction was completed.Step 2: Preparation of calcium 2,3,4,5-tetrafluorobenzoate.The above reaction solution was slowly cooled to 5 to 10C, and a solid gradually precipitated.And after stirring at this temperature for 2 hours, it is filtered and washed with moderate amounts of cold water.To obtain 3,4,5,6-tetrafluorophthalic calcium wet material about 32g. Put solids back into a fourIn a flask, about 200 g of drinking water, 2.6 g of potassium fluoride were added, and the temperature was raised to 80-90C.Gas escapes during the reaction.After 5 hours of incubation, samples were taken and tested until the starting material was less than 0.5%.Step 3: Preparation of 2,3,4,5-tetrafluorobenzoic acid.After the end of the reaction, industrial hydrochloric acid with a concentration of 30% was added dropwise.Adjust the pH to 1.5 to 2.0, then slowly cool to 5 to 10C,The solids gradually precipitated, and the mixture was stirred for 2 to 3 hours and then filtered.Solid 2,3,4,5-tetrafluorobenzoic acid was obtained, which was weighed approximately 16.8 g after being dried.The content is 98.68% and the molar yield is 90.5%.Step 4: Mother liquor extracts 2,3,4,5-tetrafluorobenzoic acid.The above mother liquor was extracted with 100 g x 2 toluene, which could be combined in multiple batches and processed. Melting point detection: 84.5~86C |
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