Ketene (CAS NO.: ) could be produced through the following synthetic route.

The pyrolysis apparatus consists of a vertical, electrically-heated Vycor® tube (25 mm. I.D.) packed with 6-mm. lengths of Pyrex® tubing (10 mm. O.D.) and mounted in an electric furnace about 45 cm. long. Attached to the top is a 100-ml. dropping funnel with a pressure-equalizing side arm2 that has an inlet for nitrogen. A thermocouple well inside the tube holds a movable thermocouple and extends to the bottom of the heated section. The bottom of the reactor is fitted to a 500-ml. side-arm flask packed in ice. The side arm leads to two traps in series cooled in ice and to a final trap cooled in a bath of dry ice and acetone.

The hottest part of the tube, which is near the middle of the heated section, is maintained at 550° ± 10° while dry oxygen-free nitrogen is passed successively through a flowmeter and the tube at about 150 ml. per hr. for at least 30 minutes. The dropping funnel is charged with 56 g. (0.67 mole) of diketene, which is then introduced into the hot tube at a rate of about 0.5 ml. per min. while the nitrogen flow continues. Essentially pure ketene, yield 26–31 g. (46–55%), collects in the dry-ice trap as a colorless or nearly colorless liquid. The ketene is distilled directly from this trap for use in reactions.

If the ketene is not to be used at once, drying tubes should be attached to the trap, which should then be stored at -80°. Ketene can be kept for as long as 2 weeks in this way, although some transformation to high-boiling material occurs. However, pure ketene can be readily obtained from a partially decomposed mixture by simple distillation from the trap. Caution! Do not store ketene under pressure, as an explosion may result.

Notice: Ketene (b.p. -41°) is a poisonous gas of the same order of toxicity as phosgene. All operations with ketene should be carried out in an efficient hood.