A
1-l., three-necked, round-bottomed flask equipped with an
efficient dry-ice condenser (Note
1), a
mechanical stirrer, and a
gas-inlet tube is immersed in an
acetone–dry ice bath, and
600 ml. of anhydrous ammonia is introduced. After replacing the inlet tube with a stopper, the cooling bath is lowered but kept beneath the flask. To the slowly stirred
ammonia is added
0.5 g. of hydrated iron(III) nitrate. Air, dried by passing through
calcium chloride, is bubbled through the solution for about 10 seconds (Note
2) after a small piece of freshly cut
sodium is added (Note
3). Once
hydrogen evolution has ceased, the blue color is discharged, leaving a finely divided, black precipitate. Small pieces of freshly cut
sodium are then added over a 20 minute period until 36.0 g. (1.56 g.-atom) has been added. After the formation of
sodium amide is complete (Note
4), the stopper is replaced with a
pressure-equalizing dropping funnel containing
76.1 g. (0.499 mole) of chloroacetaldehyde diethyl acetal (Note
5), and the addition is made over a period of 20 minutes (Note
6). After 30–60 minutes the mixture becomes light gray, and
120 g. (1.10 mole) of freshly distilled ethyl bromide is added rapidly through the addition funnel (Note
7). The mixture is stirred vigorously for 2.5 hours, after which
30 ml. of cooled, saturated ammonium chloride solution is
cautiously added through the addition funnel, followed by
120 ml. of pentane and an additional
370 ml. of the cooled, saturated ammonium chloride solution. The contents of the flask are transferred to a
2-l. separatory funnel (in the
hood); the lower aqueous layer is removed and extracted with two
75-ml. portions of pentane (Note
8). The combined organic layers are filtered through glass wool to dissipate any emulsions, dried over
magnesium sulfate, and filtered through a
coarse-fritted funnel with gentle suction into a
500-ml., round-bottomed flask. A
magnetic stirring bar is added, and the
pentane is removed by distillation at atmospheric pressure through a
20 × 2 cm. column packed with glass beads (Note
9) and fitted with a well-cooled fractionating head. With an
acetone–dry ice trap between the
receiver and the vacuum source, the yellow residue is distilled under reduced pressure (Note
10), with rapid magnetic stirring, into dry-ice-cooled receivers, giving
1-ethoxy-1-butyne as a clear, colorless liquid at
43–45° (50 mm.). A lower-boiling fraction collection at 20–42° (50 mm.) is combined with any material removed from the dry-ice trap and redistilled, yielding additional product, for a total of
30.2–32.3 g. (
62–66%) (Note
11).