2-Chloro-4-fluoro-5-nitrobenzoic acid

2252-51-9

114776-15-7

The general procedure for the synthesis of 2-chloro-4-fluoro-5-nitrobenzoic acid from 2-chloro-4-fluorobenzoic acid was as follows: 50 g of concentrated sulfuric acid and 0.8 g of the catalyst prepared in Example 1 were added to a reaction flask, followed by the addition of 10 g of 2-chloro-4-fluorobenzoic acid in batches. The reaction mixture was stirred at 25°C for 1 hour. The reaction mixture was cooled to 0°C in an ice bath, and then 5 g of fuming nitric acid was added slowly and dropwise, controlling the reaction temperature between -5 and 8°C. The reaction was continued for 5 to 8 hours until the content of 2-chloro-4-fluorobenzoic acid was less than 0.5%. The reaction mixture was slowly poured into 80 g of crushed ice and the solid product was collected by filtration. The filter cake was washed with 30 g of ice water and subsequently air-dried at 65 °C to give 12.0 g of the white solid product 2-chloro-4-fluoro-5-nitrobenzoic acid in 97.1% yield and 97.2% purity. The isomer of formula (II) was 1.1% by weight.