A mixture of 148 g. (1 mole) of cinnamic acid and 119 g. (1 mole) of thionyl chloride (Note 1) is placed in a 500-ml. Claisen flask. The side arms are stoppered, and the flask is fitted with a reflux condenser. The apparatus is mounted at an angle so that the condensate will not run into the side arm. To the top of the condenser is attached an exit tube, for evolved hydrogen chloride and sulfur dioxide, leading to a gas-absorption trap. The mixture is heated on a steam bath, cautiously at first, until no further evolution of hydrogen chloride is noted (45–60 minutes), and then allowed to cool, and 94 g. (1 mole) of phenol (Note 2) is added. The mixture is again heated on the steam bath until the evolution of hydrogen chloride has ceased (about 1 hour). It is then placed on a sand bath and brought just to the reflux temperature in order to complete the reaction and remove the hydrogen chloride more completely (Note 3).

The reaction mixture is cooled and distilled under reduced pressure (Note 4). The fraction boiling at 190–210° at 15 mm. is collected. The distillate solidifies to a pale yellow solid melting at 64° to 69° and weighing 186–200 g. (83–89%). It is purified by grinding in a mortar to a powder and washing with 500 ml. of cold 2% sodium bicarbonate solution. The residue is recrystallized from 300 ml. of 95% ethanol. The recovery is 141–168 g. (63–75%) of pure white crystals melting at 75–76°.