2.
Tetracyanoethylene is available from the Aldrich Chemical Company, Inc., or may be prepared by a simplified version of the procedure of Carboni.
2 In the simplified version,
99 g. of molten malononitrile is added to 450 ml. of cold water in the apparatus of Part A. This is followed by about 250 g. of ice and
158 ml. of bromine. The
bromine is added during 5–10 minutes, and during the addition enough ice (about 200 g.) is added to maintain the temperature at 10–15°. The mixture is stirred at 20° for one hour. A heavy layer of
dibromomalononitrile is separated, and the aqueous layer is extracted with two
50-ml. portions of 1,2-dichloroethane. The
dibromomalononitrile and the extracts are combined, dried over
magnesium sulfate, and added to
750 ml. of dry 1,2-dichloroethane in the flask of Part B. Twenty grams of
copper power is added, and the mixture is heated to gentle reflux with stirring. An exothermic reaction generally occurs; when it subsides, or after about 10 minutes, a second 20-g. portion is added, and this process is continued until 120 g. has been added. The mixture is refluxed a total of 4-6 hours. The solids are separated from the hot mixture on a
fluted filter, which is washed with a little hot
1,2-dichloroethane. The filtrate is stored overnight at 0–5°. Nearly colorless
tetracyanoethylene crystallizes out. It is separated on a
Büchner funnel, washed with a little
1,2-dichloroethane, and dried in a
vacuum desiccator; weight
29–38 g. (
30–40%). It is over 98% pure as judged by its ε
max (pure
tetracyanoethylene has λ
maxCH2Cl2 277 mμ (ε 12,050), 267 mμ (ε 13,600)). It is pure enough for most purposes, but can be sublimed at 1 mm. (bath 130–140°) if very pure material is needed (private communication from E. L. Martin and H. D. Carlson via B. C. McKusick).