Concentrated sulfuric acid (12 mL) was slowly added to concentrated nitric acid (1.6 mL) under cooling conditions in an ice bath and the reaction mixture was kept stirring for 5 min at 0 °C. Subsequently, 3-chlorobenzoic acid (3 g) was added in batches over 5 min, and the temperature of the reaction system was gradually brought to room temperature with continuous stirring for 1 h. The reaction was carried out in an ice bath under cooling conditions. Upon completion of the reaction, the reaction solution was slowly added dropwise to ice-cooled water, and the precipitated solid product was collected by filtration and washed thoroughly with cold water to finally obtain a white solid 3-chloro-5-nitrobenzoic acid (Compound 0004-1, 2.65 g).
