Organic Syntheses, Coll. Vol. 4, p.953 (1963); Vol. 39, p.68 (1959).
Caution! Because hydrogen cyanide
is formed in this reaction, all operations up to the recrystallization of the product should be carried out in a good hood
. Contact of tetracyanoethylene
with the skin should be avoided.
A solution of 26.6 g. (28 ml., 0.22 mole) of N,N-dimethylaniline
in 65 ml. of dimethylformamide
is placed in a 250-ml. beaker
clamped about 30 cm. above the base of a ring stand. The beaker is provided with a mechanical stirrer
. An iron ring
is attached to the ring stand below the beaker so that the temperature of the reaction mixture can be controlled by raising or lowering an ice bath
or hot water bath
. Recrystallized tetracyanoethylene (p. 877) (25.6 g., 0.20 mole)
is added in small portions over a period of about 5 minutes with good stirring. The rate of addition is such as to maintain the temperature at 45–50°, and occasional cooling with an ice bath may be necessary to keep the temperature within this range.
When all the tetracyanoethylene
has been added, the reaction mixture is stirred at 45–50° for 10 minutes, and heat is supplied as needed by a water bath. p-Tricyanovinyl-N,N-dimethylaniline
generally crystallizes out as a dark-blue solid during this period. At the end of the heating period, the mixture is chilled in an ice bath for 30 minutes. The tricyanovinyl compound is collected on a Büchner funnel
, pressed dry with the help of a filter dam, and washed successively with 20 ml. of methanol
and 40 ml. of ether
. It weighs 25–30 g.
after being dried in air.
The crude product is purified by recrystallization from 160–180 ml. of acetic acid
. The solution (Note 1)
is allowed to cool slowly to room temperature, and p-tricyanovinyl-N,N-dimethylaniline
is collected on a Büchner funnel and washed successively with 20 ml. of methanol
and 40 ml. of ether
. The product, 23–26 g.
), is obtained as dark-blue needles, m.p. 173–175° (Note 2)
The acetic acid
solution is so deep a red color that it is necessary to hold the flask over a bright light in order to determine when all the solid has dissolved. The solution will dye the skin with a fast red color.
Although the crystals have a very dark blue appearance, the solutions are deep red; in acetone
517 mμ (ε 41,500).
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