A
1-l., four-necked, round-bottomed flask equipped with a
sealed mechanical stirrer, a
thermometer, and a
gas-inlet tube is charged with
145 g. (1.00 mole) of 2-phenylbutyronitrile (Note
1),
2.3 g. (0.010 mole) of benzyltriethylammonium chloride (Note
2), and
50 ml. of dimethyl sulfoxide (Note
3). The gas-inlet tube is adjusted to extend below the surface of the liquid, and a
gas-exit tube is attached to the flask. A slow stream of
acetylene (Note
4) is passed through the gas-inlet tube into the flask, removing the air. After 5 minutes,
56 g. of finely powdered potassium hydroxide is added and stirring is begun.
Acetylene is introduced at the rate of 15–20 l./hour. An exothermic reaction occurs; the temperature rises to 70–80° and is held in this range with a cold water bath (Note
5). After 40–60 minutes, a warm bath is required to maintain the temperature of the reaction mixture at 60–70°, and stirring is continued for an additional 20–30 minutes (Note
6). The mixture is cooled to room temperature, the inlet tube is replaced with a
pressure-equalizing dropping funnel, and 500 ml. of water is added slowly (Note
7). The resulting dark-brown mixture is transferred to a
separatory funnel and washed twice with
200-ml. portions of benzene. The
benzene layers are combined and washed successively with 200 ml. of water,
100 ml. of 10% hydrochloric acid, and 200 ml. of water. The organic layer is dried over anhydrous
magnesium sulfate, and the
benzene is removed by distillation at reduced pressure. The residual oil is distilled through a
short Vigreux column, giving
125–135 g. of crude product, b.p.
115–125° (13 mm.). Redistillation of this product through a Vigreux column gives
101–107 g. (
59–63%) of colorless
2-phenyl-2-vinylbutyronitrile, b.p.
110° (8 mm.),
n25D 1.5157 (Note
8).