In a reaction vessel equipped with a mechanical stirrer, a solution of 2-methylbenzoic acid (10.00 g, 73.45 mmol, 1.0 equivalent) in concentrated sulfuric acid (15 mL) at room temperature, bromine (17.6 g, 110.14 mmol, 1. 5 equivalents) was added dropwise over 10 minutes and stirred at 25 ° C. for 20 hours. The reaction solution was injected into ice water (60 ml), and the precipitated solid was filtered, washed with water (20 mL), and air-dried at 60 ° C. overnight to obtain a bromo compound (15.2 g, 97%, addition rate: 95.7).5-Br body / 3-Br body = 62: 38). The obtained crude bromo compound (3 g) was dissolved in ethanol (9 mL) at 70 ° C., cooled to 20 ° C., and stirred at the same temperature for 30 minutes at 10 ° C. or lower for 3 hours. The precipitated crystals were filtered and air-dried at 60 ° C. overnight to obtain 5-Bromo-2-methylbenzoic acid(1.19 g, 5-Br / 3-Br = 91: 9, total yield: 38.5%).
