In a 6-liter reactor equipped with a condenser, a central mechanical stirrer, and a thermometer, introduce 575 g (2.5 mol) of methyl 4-bromo-3-methylbenzoate, 3 liters of methylene chloride, 494 g (2.75 mol) of N-bromosuccinimide and 17 g of benzoyl peroxide (0.05 mol; 70percent in water). Heat the mixture at reflux under irradiation with a 1000-watt lamp for 10 h. Wash the mixture twice with 1 liter of water, then with 1 liter of saturated sodium chloride solution. Evaporate the methylene chloride. Recrystallize the crude product obtained from heptane. This gives 596 g of 4-bromo-3-bromomethyl-benzoic acid methyl ester as off-white crystals.
