A solution of
sodium amide in liquid ammonia is prepared according to a procedure previously described (Note
1) in a
1-l. three-necked flask (Note
2) equipped with a
cold-finger condenser (cooled with Dry Ice) attached through a
soda-lime tower to a
gas absorption trap2 and an inlet tube. Anhydrous
liquid ammonia (500 ml.) is introduced from a commercial cylinder through the inlet tube, and
0.5 g. of hydrated ferric nitrate is added, followed by
38 g. (1.65 g. atoms) of clean, freshly cut sodium (Note
3). The inlet tube is replaced with a
100-ml. dropping funnel, and the mixture is agitated manually (Note
2) until all the
sodium is converted into
sodium amide, after which
76.5 g. (0.50 mole) of diethylchloroacetal (Note
4) is added over a period of 15–20 minutes. The mixture is swirled for an additional period of 15 minutes, after which the
ammonia is evaporated in a stream of pure
nitrogen. The flask is cooled to −70° in a
Dry Ice-trichloroethylene bath (Note
5), and
325 ml. of a saturated solution of sodium chloride which has been cooled to −20° is added all at once and as rapidly as possible with vigorous agitation (Note
6). The flask is then fitted with a still head connected to a trap cooled to −70° with Dry Ice, and the contents of the flask are slowly heated to 100° on a
steam bath (Note
7). The condensate is allowed to warm to 0°, after which the trap is again cooled to −70° and the mixture is neutralized by the dropwise addition of a saturated aqueous solution of
sodium dihydrogen phosphate. The aqueous layer is frozen by cooling with Dry Ice, and the supernatant liquid is decanted and dried over about
4 g. of anhydrous calcium chloride. The drying agent is removed by filtration, and the filtrate is distilled (Note
8) through a
column containing a 20-cm. section packed with glass helices at partial reflux, yielding
20–21.2 g. (
57–60%) of
ethoxyacetylene, b.p.
49–51°/749 mm.,
nD25 1.3790 (Note
9), (Note
10), (Note
11), and (Note
12).