Dimethyl Sulfoxide → 2,3,4,5-Tetrafluorobenzoic acid

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Reaction Conditions

Reaction Steps

A 22 liter flask was charged with 2.085 kg tetrafluorophthalic acid followed by 8.4 liter dimethylsulfoxide and 303 g triethylamine. The reaction mixture was warmed with stirring over a 50 minute period to 118° C. The resulting solution was stirred at 115°-118° C. for another 45 minutes before ice bath cooling was applied. When the temperature had reached 25° C. the solution was added with stirring to a mixture of 10 kg ice, 8 liter demineralized water, 8.4 liter n-butyl ether and 10 liter toluene in a 50 liter flask. Sulfuric acid (99%) was added dropwise to the mixture to bring the pH to 2. After stirring the organic layer was separated from the aqueous layer which was extracted two more times first with toluene (15 liters) and then with a mixture of toluene (7 liters) and n-butyl ether (1 liter). The combined organic extracts were back extracted three times with six liter portions of an aqueous sulfuric acid solution prepared from 360 ml 99% sulfuric acid and 18 liters demineralized water. The organic extract was treated with anhydrous sodium sulfate (2 kg) and Darco S-51 (300 g) filtered and the filtrate concentrated under reduced pressure on the rotary evaporator to a solid which was finally dried under vacuum at 35°-40° C. for 21 hours to give 1.62 kg (95%) 2,3,4,5-tetrafluorobenzoic acid; mp 82°-84° C.

Provenance & Evidence