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Org. Synth. 1945, 25, 63
DOI: 10.15227/orgsyn.025.0063
MALONONITRILE
Submitted by Alexander R. Surrey
Checked by C. F. H. Allen and J. VanAllan.
1. Procedure
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.
2. Notes
1. A heavy motor-driven stirrer is advisable, because frequently the solid that separates contains some viscous material that makes stirring difficult.
2. The addition of salt gives a lighter-colored, granular solid that can be easily removed by filtration and washed.
3. The reaction can be done in a hood, or the hydrogen chloride that is evolved can be absorbed in a gas trap.
4. Ground-glass equipment is advisable. The fractionating column is the standard modified Claisen type.
5. The submitter obtained a 70–72% yield at this point in a run of this size and 80% yields in small runs. He also obtained yields of the same order by using a mixture of phosphorus oxychloride and a small amount of phosphorus pentachloride.
3. Discussion
In addition to the methods cited previously,1 malononitrile has been prepared by the dehydration of cyanoacetamide by phosphorus oxychloride either with salt,2 as in the above procedure, or with sodium metabisulfite.3 The vapor-phase reaction of cyanogen chloride and acetonitrile has been patented.4

References and Notes
  1. Org. Syntheses Coll. Vol. 2, 379 (1943).
  2. Surrey, J. Am. Chem. Soc., 65, 2471 (1943); U. S. pat. 2,389,217 [C. A., 40, 900 (1946)].
  3. U. S. pat. 2,459,128 [C. A., 43, 3470 (1949)].
  4. U. S. pat. 2,553,406 [C. A., 45, 9081 (1951)].

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

sodium metabisulfite

hydrogen chloride (7647-01-0)

acetonitrile (75-05-8)

phosphorus pentachloride (10026-13-8)

ethylene dichloride (107-06-2)

Phosphorus Oxychloride (21295-50-1)

CYANOACETAMIDE (107-91-5)

cyanogen chloride (506-77-4)

Malononitrile (109-77-3)