反应详情

40 ml of concentrated nitric acid are added dropwise to 34 ml of concentrated sulphuric acid, while cooling with ice and stirring. 20.9 g of 2,4-dichloro-5-fluorobenzoic acid are introduced in portions into this nitrating mixture, whereupon the temperature rises to 45°-50° C. The mixture is then heated at 90°-100° C. for a further 3 hours, the mixture is cooled to room temperature and poured onto 350 ml of ice-water and the precipitate is filtered off with 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 cold with suction, washed with CH3OH/H2O and dried in vacuo at 80° C. 21.2 g of crude 2,4-dichloro-5-fluoro-3-nitro-benzoic acid are obtained. It is sufficiently pure for further reactions. Melting point: 192° C. (from toluene/petroleum ether).

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