In a
5-l. three-necked, round-bottomed flask fitted with an
efficient stirrer (Note
1), a
separatory funnel, and a
thermometer in a well is placed a solution of
500 g. (9.7 moles) of powdered 95 per cent sodium cyanide in 1.2 l. of water and
900 cc. (713 g., 12.3 moles) of acetone. The flask is surrounded by an
ice bath, and the solution is stirred vigorously. When the temperature falls to 15°,
2.1 l. (8.5 moles) of 40 per cent sulfuric acid (Note
2) is added over a period of three hours, the temperature being kept between 10° and 20°. After all the acid has been added the stirring is continued for fifteen minutes and then the flask is set aside for the salt to settle. Usually a layer of
acetone cyanohydrin forms and is decanted and separated from the aqueous layer. The
sodium bisulfate is removed by filtration and washed with three
50-cc. portions of acetone. The combined filtrate and
acetone washings are added to the aqueous solution, which is then extracted three times with
250-cc. portions of ether (Note
3). The extracts are combined with the cyanohydrin previously separated and dried with anhydrous
sodium sulfate. The
ether and
acetone are removed by distillation from a
water bath, and the residue is distilled under reduced pressure. The low-boiling portion is discarded, and
acetone cyanohydrin is collected at
78–82°/15 mm. The yield is
640–650 g. (
77–78 per cent of the theoretical amount) (Note
4).