4-Nitro-2-(trifluoromethyl)benzoic acid

433-97-6

320-37-6

A mixture of 2-trifluoromethylbenzoic acid (1 eq.) and concentrated sulfuric acid (22 eq.) was placed in a mechanical stirrer under nitrogen protection and cooled to 0-5 °C in an ice bath. Subsequently, fuming nitric acid (9.8 eq.) was slowly added dropwise at the same temperature for 60 minutes. After completion of the dropwise addition, the ice bath was removed and the reaction mixture was allowed to continue stirring at room temperature for 120 minutes. Upon completion of the reaction, the mixture was slowly poured into ice water and stirred at room temperature for 60 minutes. The suspension was collected by filtration and washed with cold water to give the crude 4-nitro-2-trifluoromethylbenzoic acid. To remove the regional isomers, the crude product was recrystallized from water to give the final pure product in 45% yield. The melting point range was 137-142°C.