A solution of
50 g. (0.42 mole) of acetophenone (Org. Syn. Coll. Vol. I, 1941, 111) in
50 cc. of pure anhydrous ether (Note
1) is placed in a dry
three-necked flask fitted with a
separatory funnel,
mechanical stirrer, and
reflux condenser (Note
2). The solution is cooled in an
ice bath,
0.5 g. of anhydrous aluminum chloride is introduced (Note
3), and
67 g. (21.5 cc., 0.42 mole) of bromine is added gradually from the separatory funnel, with stirring, at the rate of about 1 cc. per minute. The
bromine color disappears rapidly although very little
hydrogen bromide is evolved; towards the end of the reaction the solution becomes pink.
After the
bromine has been added the
ether and dissolved
hydrogen bromide are removed at once (Note
4) under reduced pressure with a slight current of air. The
phenacyl bromide remains as a solid mass of brownish yellow crystals (Note
5); the color is removed by shaking with a mixture of 10 cc. of water and
10 cc. of petroleum ether. The crystals are filtered with suction and washed several times with fresh portions of the solvent mixture, if necessary, until a white product is obtained (Note
6). The crude
phenacyl bromide weighs
74–80 g. (
88–96 per cent of the theoretical amount) and melts at
45–48°. This material is sufficiently pure for many purposes. If higher purity is desired the crude product may be recrystallized from
25–30 cc. of methanol, yielding
54–55 g. (
64–66 per cent of the theoretical amount) of white crystals melting at
49–51° (Note
7).