Synthesis of III-2-2:4-nitropyridine carboxylic acid
5.00 g (34 mmol) of 2-cyano-4-nitropyridine was dissolved in 50 g of 90% sulfuric acid and the reaction was stirred at 120°C for 2 hours. Subsequently, a solution of 5.60 g of sodium sulfite dissolved in 10 ml of water was slowly added dropwise at 20 °C to 25 °C, and the stirring was continued at the same temperature for 1 h. After that, the reaction was warmed up to 80 °C for 1 h. The reaction was completed by cooling to room temperature. Upon completion of the reaction, it was cooled to room temperature, diluted by adding 100 g of ice water, and the pH of the mixture was adjusted with sodium carbonate to about 2. The mixture was allowed to stand in a refrigerator to induce precipitation of solids. The precipitate was collected by filtration and recrystallized using a water-acetone solvent mixture to give 3.50 g of light yellow crystalline product in 62.1% yield. The melting point of the product was 157°-158°C (accompanied by decomposition).The IR (KBr) spectrum showed characteristic absorption peaks located at 1710, 1600, 1585, 1535 cm-1 .
