反应详情

40 ml of concentrated nitric acid are added dropwise to 34 ml of concentrated sulphuric acid, while cooling in ice and stirring. 20.9 g of 2,4-dichloro-5-fluorobenzoic acid are introduced in portions into this nitration mixture, during which the temperature rises to 45°-50° C. The mixture is then heated at 90°-100° C. for 3 hours, 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 was dissolved in 30 ml of hot methanol, and 150 ml of H2O are added to the solution. The precipitate is cooled, filtered off with suction, washed with CH3OH/H2O and dried in vacuo at 80° C. 21.2 g of crude 2,4-dichloro-5-fluoro-3-nitrobenzoic acid are obtained. It is sufficiently pure for the subsequent reactions. A sample recrystallized from toluene/petroleum ether provides crystals of melting point 192° C.

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