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 nitration 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 hot in 30 ml of methanol, and 150 ml of H2O were 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. The compound is sufficiently pure for the subsequent reactions. A sample recrystallized from toluene/petroleum ether gives crystals of melting point 192° C.

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 hot in 30 ml of methanol
7. addition150 ml of H2O were 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