A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1959, 39, 13
DOI: 10.15227/orgsyn.039.0013
Submitted by C. L. Dickinson and L. R. Melby1.
Checked by James Cason, Edwin R. Harris, and William T. Miller.
1. Procedure
Caution! This preparation must be carried out in a good hood because hydrogen cyanide is evolved. It is inadvisable to allow contact of tetracyanoethylene with the skin.
Urea (4.0 g., 0.067 mole) is dissolved in 50 ml. of distilled ethylene glycol (Note 1) contained in a 125-ml. Erlenmeyer flask. Finely divided recrystallized tetracyanoethylene (p. 877) (25.6 g., 0.20 mole) is added, and the flask is heated on a steam bath at 70–75° with frequent stirring by hand with a thermometer until solution is complete (about 15 minutes). The resultant brownish yellow solution is then cooled in ice water, and the precipitated dicyanoketene ethylene acetal is collected on a Büchner funnel. The acetal is first washed with two 25-ml. portions of cold ethylene glycol and then washed thoroughly with cold water to remove the ethylene glycol. The dicyanoketene ethylene acetal, which may be dried in air or in a vacuum desiccator, is obtained in the form of large slightly pink needles, m.p. 115–116.5° (Note 2); yield 21–23 g. (77–85%).
2. Notes
1. Moisture in the ethylene glycol leads to lowered yields. Satisfactory results are obtained with glycol collected at 199.5–201° from a simple distillation.
2. The color may be removed by recrystallization from ethanol after treatment with decolorizing carbon; however, the melting point is not improved and occasionally is found to be lowered.
3. Discussion
The synthesis of dicyanoketene ethylene acetal described here is a slight modification of one published recently.2 The procedure has been applied successfully to the synthesis of dicyanoketene dimethyl acetal and dicyanoketene diethyl acetal.2
Dicyanoketene ethylene acetal reacts with tertiary amines to give quaternary ammonium inner salts.2 Similarly, it reacts with sulfides to give sulfonium inner salts.2 These products are generally solids that can be used to characterize tertiary amines and sulfides. Dicyanoketene acetals can be converted to pyrimidines, pyrazoles, or isoxazoles in one step.3

References and Notes
  1. Contribution No. 481 from Central Research Department, Experimental Station, E. I. du Pont de Nemours & Co., Wilmington, Delaware.
  2. Middleton and Engelhardt, J. Am. Chem. Soc., 80, 2788 (1958).
  3. Middleton and Engelhardt, J. Am. Chem. Soc., 80, 2829 (1958).

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


ethanol (64-17-5)

hydrogen cyanide (74-90-8)

decolorizing carbon (7782-42-5)

ethylene glycol (107-21-1)

urea (57-13-6)

Dicyanoketene ethylene acetal (5694-65-5)

dicyanoketene dimethyl acetal

dicyanoketene diethyl acetal

Tetracyanoethylene (670-54-2)