A
500-ml. three-necked flask is fitted with a
reflux condenser and a
thermometer, the bulb of which reaches far enough into the flask to be covered by the liquid. A solution of
46.0 g. (0.205 mole) of α-phenylcinnamic acid (p. 777) (Note
1) in
280 ml. (307 g., 2.38 moles) of quinoline (Note
2) is added to the flask along with
4.0 g. of copper chromite.
2 The reaction flask is heated by means of a mantle or an
oil bath until the temperature of the reaction mixture reaches 210–220°. The mixture is kept within this temperature range for 1.25 hours. The solution is then cooled immediately and added to
960 ml. of 10% hydrochloric acid in order to dissolve the
quinoline (Note
3). The product is extracted from this mixture with two
200-ml. portions of ether followed by a 100-ml. portion. The combined
ether extracts are filtered to remove particles of catalyst, washed with
200 ml. of 10% sodium carbonate, and dried over anhydrous
sodium sulfate. The dry solution is removed from the drying agent by filtration and heated on a
steam bath to distil the
ether. The residue is dissolved in a
hexane fraction, b.p.
60–72° (Skellysolve B); the solution is cooled to 0° and filtered to remove
trans-stilbene, if any. The hydrocarbon solvent is removed by distillation, and the
cis-stilbene is distilled. The yield is
23–24 g. (
62–65%), b.p.
133–136° /10 mm.,
95–97° /1 mm.;
n25D 1.6183–1.6193,
n20D 1.6212–1.6218 (Note
4).