A.
tert-Butylmalononitrile. A dry,
2-l., three-necked flask equipped with a
thermometer,
mechanical stirrer, and a
Claisen adapter fitted with a
dropping funnel and
condenser protected with a drying tube is charged with
200 ml. of nitromethane (Note
1). The flask is cooled to 0° in an
ice–salt bath (Note
2), and anhydrous powdered
aluminum chloride (90.0 g., 0.674 mole) is added, with slow stirring, through a
powder funnel that temporarily replaces the thermometer. The temperature may rise to
ca. 50° but quickly drops to 0°. A solution of
45.0 g. (0.682 mole) of malononitrile (Note
3) in
50 ml. of nitromethane is added through the dropping funnel at a rate such that the temperature is kept below 10° (approximately one hour). This is followed by slow, dropwise addition of a solution of
150 g. (1.62 moles) of tert-butyl chloride in 50 ml. of nitromethane at a rate such that the temperature is maintained below 10° (approximately 3–4 hours). The reaction mixture is stirred at 0–5° for 10 hours before
1 l. of saturated sodium hydrogen carbonate (ca. 80 g. in 1000 ml. of water) is added slowly and cautiously (still in the cold), keeping the temperature below 10°. The mixture is poured into a
3 or 4 l. beaker and solid
sodium hydrogen carbonate (ca. 100 g.) is added in
small portions, with stirring. The organic phase is separated, and the aqueous layer extracted with three half-volume portions of
dichloromethane, which are concentrated on a
rotary evaporator, combined with the organic phase, and concentrated further. The resultant brown oil is subjected to steam distillation. The first fraction is collected using a cold water condenser until solidification is observed in the condenser, at which time warm water is passed through the condenser and the
receiver is changed (Note
5). The product is collected until occasional passage of cold water through the condenser no longer causes apparent solidification. At this point, the receiver is changed again, and a third fraction (
ca. 500 ml.) is collected. The middle fraction is cooled in ice and filtered with vacuum through a
medium fritted glass funnel, yielding
48–50 g. of light-yellow product. Extraction of the filtrate with two half-volumes of
diethyl ether followed by evaporation gives an additional small amount (
ca. 2 g.) of product. Another small crop of product may be gleaned from the first and third steam distillation fractions by separating any organic phase, removing distillable material on a rotary evaporator, cooling, and filtering the resulting solid. The total combined yield of crude product is
54–58 g. (
65–70%). Further purification is accomplished by careful sublimation at 80–90 mm. (
ca. 85°), giving
52–56.5 g. (
63–68%) of white, waxy dinitrile, m.p.
76–79° with softening at 71°.