In a 1-l. three-necked flask having ground-glass joints are placed 500 g. (569 ml., 4.72 moles) of o-xylene, 12 g. of clean iron filings, and a crystal of iodine (Note 1). The flask is fitted with a dropping funnel, a stirrer (Note 2), and a condenser; a thermometer is suspended through the condenser on a platinum or Nichrome wire and arranged so that the bulb extends beneath the surface of the liquid. The top of the condenser is connected to a gas-absorption trap. The mixture is stirred and cooled in an ice-salt mixture, preferably under a hood. Six hundred and sixty grams (4.13 moles) of bromine is added drop-wise over a 3-hour period; during this time the internal temperature is maintained at 0° to −5° (Note 3). After all the bromine has been added the reaction mixture is allowed to stand overnight. It is poured into water and washed successively with a 500-ml. portion of water, two 500-ml. portions of 3% sodium hydroxide solution (Note 4), and one 500-ml. portion of water. The product is then steam-distilled; about 8 l. of distillate is collected (Note 5). The organic layer is separated from the water and dried over calcium chloride. The 4-bromo-o-xylene is distilled through a short column under reduced pressure, and the fraction boiling at 92–94°/14–15 mm. (n²²D 1.5558) is collected. The yield is 720–745 g. (94–97%, based on bromine) (Note 6).