A.
α-Bromocinnamic aldehyde. A mixture of
44 g. (0.33 mole) of cinnamic aldehyde and
167 ml. of acetic acid in a
500-ml. three-necked round-bottomed flask, surrounded by a cold-water bath and fitted with a stirrer, reflux condenser, and dropping funnel, is stirred vigorously while
17.1 ml. (53.5 g., 0.33 mole) of bromine is added. This is followed by the addition of
23 g. (0.17 mole) of anhydrous potassium carbonate. When the evolution of gas has ceased, the mixture is refluxed for 30 minutes, then cooled and poured into 435 ml. of water in a
1-l. flask; a lower, reddish layer of crude α-bromoaldehyde separates. The flask is stoppered, cooled under running water, and shaken vigorously. The resulting granular solid is filtered with suction and dissolved without drying by warming with
220 ml. of 95% ethanol. After the addition of 50 ml. of water, the solution is warmed until it becomes clear and is then set aside to crystallize at room temperature and finally in a refrigerator.
α-Bromocinnamic aldehyde separates as nearly colorless needles, which are filtered with suction, rinsed with
17 ml. of 80% ethanol, and air-dried. The yield of product melting at
72–73° is
52–60 g. (
75–85%) (Note
1).