(CAS NO.: ), which is also known as 4-bromobenzaldehyde, could be produced through the following synthetic routes.

In a 1-l. three-necked flask fitted with a mechanical stirrer, a reflux condenser, a thermometer, and a dropping funnel is placed 100 g. (0.58 mole) of p-bromotoluene. The stem of the dropping funnel and the thermometer should reach nearly to the bottom of the flask. The upper end of the condenser is connected to a gas absorption trap. The flask is heated with stirring in an oil bath until the temperature of the liquid reaches 105°. The liquid is illuminated with an unfrosted 150-watt tungsten lamp, and 197 g. (61.8 cc., 1.23 moles) of bromine is added slowly from the separatory funnel. About one-half of the bromine is added during the first hour, during which time the temperature is kept at 105–110°. The rest is added during about two hours while the temperature is raised to 135°. When all the bromine has been added the temperature is raised slowly to 150°.

The crude product is transferred to a 2-l. flask and mixed thoroughly with 200 g. of powdered calcium carbonate. About 300 cc. of water is added and the mixture is heated cautiously and then refluxed for fifteen hours to effect hydrolysis. The product is then distilled in a rapid current of steam; the distillate is collected in 500-cc. portions and cooled; and the p-bromobenzaldehyde is collected and dried in a desiccator. From the first liter of distillate 50–60 g. of p-bromobenzaldehyde melting at 55–57° is obtained. An additional 15–20 g. of product melting at 50–56° is obtained in about 2 l. more of distillate. This may be purified through the bisulfite addition compound and yields 13–18 g. of product melting at 55–57°. The total yield of pure aldehyde is 65–75 g. (60–69 per cent of the theoretical amount).