反应详情

40 ml of concentrated nitric acid are added dropwise, with ice cooling and stirring, to 34 ml of concentrated sulphuric acid. 20.9 g of 2,4-dichloro-5-fluorobenzoic acid are added in portions to this nitration mixture, the temperature increasing to 45°-50° C. The mixture is then heated for a further 3 hours at 90°-100° C. and, after cooling to room temperature, 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 precipitate is filtered off under suction when cold, 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 sufficiently pure for the further reactions. Melting point: 192° C. (from toluene/petroleum ether).

1. temperaturethe temperature increasing to 45°-50° C
2. temperatureThe mixture is then heated for a further 3 hours at 90°-100° C.
3. filtrationthe precipitate is filtered off under suction
4. washwashed with water
5. dissolutionThe moist crude product is dissolved in 30 ml of hot methanol
6. addition150 ml of H2O are added to the solution
7. filtrationThe precipitate is filtered off under suction when cold
8. washwashed with CH3OH/H2O
9. customdried at 80° C. in vacuo