In a
12-l. three-necked round-bottomed flask, fitted with a
powerful stirrer (Note
1) and a
reflux condenser, are placed
1260 g. (15 moles) of cyanoacetamide, 1 kg. of salt (Note
2), and
5 l. of ethylene dichloride. After the mixture has been stirred rapidly for 15 minutes,
800 ml. (8.75 moles) of phosphorus oxychloride is added and the mixture is refluxed for 8 hours in an
oil bath (Note
3). After the mixture has been cooled to room temperature, it is filtered and the solid is washed with
500 ml. of ethylene dichloride. The solvent is distilled from the combined filtrates in a 12-l. flask, and the residual crude nitrile is decanted into a
1-l. flask (Note
4) from any solid that may have separated. A
fractionating column,
condenser, and
fractionating receiver are attached, and the
malononitrile is distilled under reduced pressure. The fraction boiling at
113–118°/25 mm. weighs
570–654 g. (
57–66%) (Note
5). This material may be freed from a small amount of
phosphorus oxychloride which is present by redistillation. After a fore-run of about 5 ml., the
malononitrile distils smoothly at
92–94°/8 mm.