Nitric Acid → 2,4-Dichloro-5-fluoro-3-nitrobenzoic acid

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Reaction Steps

40 ml of concentrated nitric acid are added dropwise to 34 ml of concentrated sulphuric acid with ice cooling and stirring. 20.9 g of 2,4-dichloro-5-fluorobenzoic acid are introduced in portions into this nitration mixture, the temperature rising to 45°-50° C. The mixture is then heated at 90°-100° C. for a further 3 hours, cooled to room temperature and poured into 350 ml of ice water, and the precipitate is filtered off under suction and washed with water. The moist crude product is dissolved in 30 ml of hot methanol, and 150 ml of H2O are added to the solution. The cold precipitate is filtered off under suction, washed with CH3OH/H2O and dried at 80° C. in vacuo. 21.2 g of crude 2,4-dichloro-5-fluoro-3-nitro-benzoic acid are obtained. It is adequately pure for the further reactions. A sample, recrystallized from toluene/petroleum ether, yields crystals of melting point 192° C.

Provenance & Evidence