(
A) In a
500-cc. Claisen distilling flask with a low
side tube connected to a
condenser, are placed
105 g. (0.69 mole) of mandelic acid (p. 336) (m.p.
118°) and
151 g. (137 cc., 1.92 moles) of acetyl chloride. A reaction sets in without the application of heat (Note
1). As soon as a clear solution results, the flask is warmed on a
water bath and the excess
acetyl chloride is distilled. The last trace of
acetyl chloride may be removed by prolonged drying in a vacuum. The
acetylmandelic acid then crystallizes in large, round, white clusters after one or two days' standing. The yield is
130–133 g. (
97–99 per cent of the theoretical amount) (Note
2).
(
B) To the crude
acetylmandelic acid still containing some
acetyl chloride obtained as described above, is added
250 g. (149 cc., 2.1 moles) of thionyl chloride. The reaction starts at once without warming but it is necessary to reflux for four hours to complete the reaction (Note
3). The excess
thionyl chloride is then distilled and the residue distilled under reduced pressure (Note
4). The yield is
115–120 g. (
79–82 per cent of the theoretical amount) of almost colorless liquid boiling at
125–130°/10 mm. (
150–155°/33 mm.).