A 1-l. three-necked, round-bottomed flask equipped with a mechanical stirrer, a gas-inlet tube, and a dropping funnel is charged with 200 ml. of pyridine (Note 1) and 9.9 g. (0.10 mole) of copper(I) chloride (Note 2) which partially dissolves in pyridine, forming a yellow suspension (Note 3). Oxygen is bubbled into the suspension rapidly for 10 minutes; the suspension changes into a deep-green turbid solution (Note 4). A solution of 27 g. (0.25 mole) of 1,2-benzenediamine (Note 5) in 300 ml. of pyridine is added slowly from the dropping funnel during 2 hours, while vigorous stirring and bubbling of oxygen are continued (Note 6), (Note 7). The reaction mixture is transferred to a 1-l., round-bottomed flask, and pyridine is removed under reduced pressure (20 mm.) using a rotary evaporator until a deep-green solid residue is obtained, to which 400 ml. of 6 N hydrochloric acid and 400 ml. of dichloromethane are added. The mixture is shaken until the solid is dissolved, and the lower layer is separated (Note 8). The upper layer is extracted with three 100-ml. portions of dichloromethane. The combined dichloromethane solution is washed with 100 ml. of 5% aqueous sodium hydrogen carbonate, dried over anhydrous sodium sulfate, and evaporated. The brown residue is dissolved in 600 ml. of warm benzene, and the solution is filtered through filter paper. When the benzene is evaporated, 23–24 g. (88–93%) of crude product is obtained as a brownish solid, which is recrystallized twice from methanol (7 ml. for 1 g. of the crude material), yielding 19–20 g. (73–77%) of (Z,Z)-2,4-hexadienedinitrile as colorless needles, m.p. 128–129° (Note 9).