A 1-l. three-necked flask is fitted with a stirrer, a condenser, a dropping funnel, and a heating mantle. Sixty-one grams (1.25 moles) of sodium cyanide and 100 ml. of distilled water are added, and the mixture is warmed with stirring for about 15 minutes while the sodium cyanide dissolves. Then 400 ml. of methanol (Note 1) is introduced, and the mixture is rapidly heated to gentle reflux. Fifty grams (0.42 mole) of benzyl cyanide is added all at once, followed by dropwise addition of a solution of 53 g. (0.50 mole) of benzaldehyde and 30 g. (0.26 mole) of benzyl cyanide (Note 2). The addition requires about 40 minutes, during which time the reaction mixture turns from yellow to green and crystalline 2,3-diphenylsuccinonitrile begins to separate (Note 3). The reaction mixture is stirred at gentle reflux for 30 minutes after the addition is complete. The reaction mixture, now blue in color, becomes brown as it is cooled to room temperature.

The nitrile is separated from the cooled reaction mixture by suction filtration, washed successively with 150-ml. portions of 75% aqueous methanol, water, 75% aqueous methanol, and ether, and dried in air overnight. It is obtained as a colorless solid that weighs 84–89 g. (72–77%) and melts over a range of 1–2° between 202° and 206° (Note 4). It is the meso-isomer of 2,3-diphenylsuccinonitrile mixed with a small amount of the dl-isomer. Recrystallization from glacial acetic acid (about 27 ml. per g.), followed by washing with 150-ml. portions of water, 75% aqueous methanol, and ether, yields 79–84 g. (68–72%) of the pure meso-isomer, m.p. 238–239° (Note 5).

Two hundred and five grams (1 mole) of α-phenylcinnamonitrile,⁴ 2250 ml. of methanol, and 750 ml. of ether are placed in a 5-l. round-bottomed flask fitted with a two-necked adapter supporting a 1-l. separatory funnel and reflux condenser. The α-phenylcinnamonitrile is dissolved by gentle heating, and the solution is heated under reflux. A solution of 274 g. (4 moles) of 95% potassium cyanide in 600 ml. of water (which has been preheated to 45°) is added rapidly from the separatory funnel (Note 1). A small amount of potassium cyanide precipitates. The solution is heated under reflux for 1 hour, after which a solution of 154 g. (2 moles) of ammonium acetate in 250 ml. of water is added rapidly from the separatory funnel (Note 2). Heating is discontinued, and the mixture is allowed to stand for 24 hours. The slightly orange-yellow crystalline product is collected on a Büchner funnel and washed, first with two 300-ml. portions of water at 60° to remove inorganic salts, then with 800 ml. of 70% methanol for removal of water and some unreacted α-phenylcinnamonitrile, and finally with two 300-ml. portions of ether for further drying. The colorless needles thus obtained consist of a mixture of the stereoisomeric α,α'-diphenylsuccinonitriles and, after drying at room temperature for 6 hours, weigh 213–218 g. (92–94%). This mixture of stereoisomers melts over a 1–2° range in the region of 202–206° (Note 3).

The mixed dinitrile can be recrystallized from glacial acetic acid (using 27 ml. per g.) to give pure meso-α,α'-diphenylsuccinonitrile. Residual acetic acid is removed readily by washing the crystalline product with small portions of water, aqueous methanol (70%), and ether; yield 95–98% (based on mixed dinitrile); m.p. 240–241.5° (cor.).