In a 2000ml three-necked flask, 400g of concentrated sulfuric acid,p-fluorobenzotrifluoride 400g, lithium bromide 10g, ferric bromide 20g, tetrabutylammonium bromide 10g, Bromine 234.14g, temperature control 35-45 ° C, the reaction 6h, GC detection of raw materials 0.36percent. Cooled to below 30, transferred to 2000ml separation funnel, stationary 1h, the acid was separated, the crude product was placed in 2000 ml bottle,1000g of water was added under stirring, dropping 10 percent sodium hydroxide solution to adjust PH = 7,548.6 g of 3-bromo-4-fluorobenzotrifluoride was isolated at a constant rate of 92.56percent with 97.9 percent.
