Hydrogen Peroxide → 2,4-Dichloro-5-fluorobenzoic acid

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Reaction Steps

26.8 g (0.1 mol) of 2,4-dichloro-5-fluorobenzophenone are dissolved in 250 g of 96% sulfuric acid, and 17 g of 30% hydrogen peroxide solution are added at 0° C., with thorough mixing, in such a way that the temperature does not exceed 40° C. When the metered addition is complete, the temperature is allowed to drop to 20° C. and the mixture is stirred for 5 h at this temperature. If the conversion is incomplete, a further 5 g of hydrogen peroxide solution are metered in (T<40° C.) and the mixture is diluted with 1000 g of water after a further 3 h of reaction time and is subsequently stirred for 2 h. The 2,4-dichloro-5-fluorobenzoic acid which has precipitated out is filtered off and purified by recrystallization (water) to give 17.8 g (0.0852 mol, 85%) of 2,4-dichloro-5-fluorobenzoic acid melting at 144°-146° C.

Provenance & Evidence