To a beaker 225 mL of very cold conc, sulfuric acid and 122 g of potassium nitrate are added with stirring, the clear solution is cooled to 20°C and the beaker is immersed in an ice bath. With vigorous stirring 30 mL of chlorobenzene is added to the solution, the temperature should be maintained below 50°C, after the addition stir for 10 minutes and then heat the mixture at 100-105°C for 2h. The still hot solution is poured into 1L of ice water slush, filtered and washed with 300 mL of cold water. The crude product is recrystallized twice from warm methanol.
The nitrating solution
Addition of the chlorobenzene
Pouring the solution into the ice
First recrystallization from methanol
Second recrystallization from methanol
The pure recrystallized product