反应详情

温度

170 °C

2,6-Dichloroaniline (22.0 g; 0.136 mol) was added cautiously to concentrated sulphuric acid (50 ml) under nitrogen, with cooling and stirring. When addition was complete the reaction mixture was heated under nitrogen at 170° C. for 5 hr, then allowed to cool to 50° C. before pouring into cold water (4° C.). The precipitate was filtered and then heated with decolourising charcoal (2 g) in boiling water (500 ml) for 15 min. After filtration the solvent was removed and the crude product was recrystallised from water to give a crystalline solid, which was dried over silica gel overnight, to give 3,5-dichlorosulphanilic acid as a white powder. Yield 13.7 g (42%).

1. temperaturewith cooling
2. additionWhen addition
3. temperatureto cool to 50° C.
4. filtrationThe precipitate was filtered
5. temperatureheated with decolourising charcoal (2 g)
6. customfor 15 min
7. filtrationAfter filtration the solvent
8. customwas removed
9. customthe crude product was recrystallised from water
10. customto give a crystalline solid, which
11. customwas dried over silica gel overnight