A suspension of 4-Amino-3-methylbenzoic acid (73 g, 0.483 mol) in water (411 mL) and 47percent HBr (486 mL) was stirred at 25 ℃ for 1 h and then the reaction mixture was cooled to -2 ℃. A solution of sodium nitrate (32 g, 0.463 mol) in water (100 mL) was added to the reaction mixture over 15 min, maintaining the temperature at -1 ℃ to -2°C. The reaction mixture was stirred at -1 ℃ to -2 ℃ for 1.5h. The reaction mixture was added slowly to a suspension of copper(l)bromide (73 g, 0.508 mol) in water (73 mL) and aqueous HBr (73 mL). The reaction mixture was stirred at 250C for 1 h and then digested at 70 °C for 1 h. The solid was filtered, washed with water till the pH of the filtrate was 7 and dried to obtain 4-Bromo-3-methylbenzoic acid.
