A. N-Ethyl-p-chloroformanilide. In a 300-ml. round-bottomed flask, equipped with a side tubulature just large enough to accommodate a thermometer, are placed 63.8 g. (0.50 mole) of p-chloroaniline and 111 g. (0.75 mole) of triethyl orthoformate (Note 1), and then 2.0 g. (0.02 mole) of concentrated sulfuric acid is added with mixing. The flask is attached to a 30-cm. column 2 cm. in diameter packed with glass helices (Note 2), which is surmounted by a distillation head equipped with a thermometer and condenser. A thermometer is connected through a slip joint made from a short section of rubber tubing to the side tubulature so that its bulb is in the reaction mixture; then the flask is heated in an oil bath. When the temperature of the oil bath reaches 115–120°, the reaction mixture begins to boil, and ethanol soon begins to distil at a vapor temperature of 78–80° at the top of the column. During the course of about 1 hour the bath temperature is raised to about 175°. This promotes a steady distillation of ethanol at a rate which begins to decrease after 30 minutes. The amount of ethanol that distils (70–75 ml.) is always in excess of the stoichiometric amount. Finally, the reaction mixture is kept in the oil bath at 175–180° for 30 minutes (Note 3); an additional small amount of volatile material distils during this time.

After the reaction mixture has cooled somewhat the flask is disconnected from the column, a Claisen head is attached, and the product is distilled at reduced pressure (Note 4). After a fore-run of about 20 g. (not readily condensed below 40 mm. pressure), the faintly yellow product is collected at 124–126°/3 mm., weight 73–79 g. (80–86%), n_D25 1.5525–1.5540 (Note 4).

B. N-Ethyl-p-chloroaniline. In a 500-ml. round-bottomed flask are placed 70 g. (0.38 mole) of N-ethyl-p-chloroformanilide and 170 ml. of 10% hydrochloric acid. The mixture is heated under reflux for 1 hour, cooled, then neutralized, and finally made basic with 15% potassium hydroxide solution. The lower layer of N-ethyl-p-chloroaniline is separated, and the aqueous layer is saturated with potassium carbonate and extracted with two 200-ml. portions of ether. The ether extracts are combined with the bulk of the product, washed with two 100-ml. portions of water, and then dried over calcium chloride. After the ether has been removed by distillation, the residue is distilled at reduced pressure from a 125-ml. Claisen flask. N-Ethyl-p-chloroaniline is collected at 108–110°/5 mm. or 149–150°/40 mm., n_D25 1.5650–1.5661, weight 52–55 g. (87–92%) (Note 5).