The general procedure for the synthesis of 2,5-dibromo-4-nitro-1H-imidazole from 4-nitroimidazole was as follows: 4-nitroimidazole (100 g, 884 mmol), sodium bicarbonate (164 g, 1.94 mol), and water (500 ml) were mixed with vigorous stirring. Subsequently, bromine (106 ml, 2.07 mol) was added slowly and dropwise. The reaction mixture was stirred at room temperature (23°C to 25°C) for 6 h. Vigorous foaming was observed during the dropwise addition. Next, the reaction mixture was heated to 50°C to 55°C and stirring was continued for 4 hours. Upon completion of the reaction, water (400 ml) and concentrated hydrochloric acid (80 ml) were sequentially added to the mixture under ice bath cooling (temperature controlled at 10°C or lower) and stirring was continued for 1 hour. The resulting crystals were collected by filtration. The resulting crystals were first washed with 400 ml of water on filter paper, followed by two dispersion washes with 800 ml of water. Finally, the crystals were air dried at 50°C for 16 hours. A light yellow crystalline product of 213 g was obtained with a yield of 88.9%. The characteristic absorption peaks of the infrared spectrum (KBr press method) of the product were 3074, 1548, 1468, 1392, 1361, 1345, 1310, 1259, 1172, 1066, 975, 830, 667 cm-1.
