In a
2-l. round-bottomed flask fitted with a
three-holed stopper bearing a
mechanical stirrer, a
separatory funnel, and a gas outlet tube leading to a
hood (Note
1) are placed
1 l. of anhydrous ether (Note
2) and
156 g. (4 moles) of finely ground sodium amide (p. 778) (Note
3). The flask is surrounded by a well-packed
ice-salt bath. To the vigorously stirred mixture
232 g. (4 moles) of dry acetone (Note
4) is added, dropwise, during a period of 3 hours. With the flask cooled to −10° (Note
5), a slow current of
acetylene (Note
6) is passed through the reaction mixture for 2 hours to sweep out the
ammonia. The three-holed stopper is then replaced by a two-holed stopper having a stopcock and an inlet tube reaching to the bottom of the flask and connected with a cylinder of
acetylene. The stopper is wired in. The mixture is placed in an ice-salt mixture (Note
5), the whole being mounted on a shaking machine and agitated vigorously for 10 hours; the mixture is kept under a pressure of 10 lb. of
acetylene. Every 30 minutes the pressure is released by means of the stopcock, to sweep out
ammonia formed from small amounts of previously unreacted
sodium amide.
The reaction mixture is poured cautiously into 800 g. of crushed ice and acidified in the cold by the addition of
400 ml. of 10 N sulfuric acid (Note
7). The
ether layer is separated and the aqueous layer extracted twice with
100-ml. portions of ether. The combined ethereal solutions are dried over
100 g. of anhydrous potassium carbonate, and the filtered solution is fractionated (Note
8). The portion boiling at
103–107° is collected; any low-boiling fraction is dried and redistilled. The total yield is
135–155 g. (
40–46%) of a colorless product that boils at
103–107° (Note
9), (Note
10), and (Note
11).