The general procedure for the synthesis of N1-(4,5-dichloro-2-nitrophenyl)acetamide from N-(3,4-dichlorophenyl)acetamide was as follows: 3,4-dichloroacetanilide (II) (150 g, 0.74 mol) was slowly added to a reactor containing sulfuric acid (270 g, 99%, 2.7 mol) at 13 °C, stirred for 0.5 h and then cooled to 8 °C. Subsequently, fuming sulfuric acid (422 g, 31.1%, 4.61 mol) was slowly added to obtain a mixture. The sulfuric acid concentration of this mixture was 104%, where the molar ratio of 3,4-dichloroacetanilide (II) to sulfuric acid was 1:10. The mixture was further cooled to 3 °C and nitric acid (51 g, 98%, 0.79 mol) was slowly added over a period of 5 hours. The progress of the reaction was monitored by thin layer chromatography (TLC).3,4-Dichloroacetanilide was completely consumed within 1 h to give the product mixture. The product mixture was carefully poured into a mixture of 1650 g of ice with 200 ml of water, maintained at a temperature below 15 °C and stirred for 15 min to form a dispersion. The dispersion was filtered to give a residue containing 2-nitro-4,5-dichloroacetanilide (I). The residue was washed with water until no residual acid remained and dried to give 2-nitro-4,5-dichloroacetanilide (I) (174 g, yield = 95.23%, HPLC purity = 97.83%).HPLC analysis showed that the product contained 1.46% III.
