Org. Synth. 1941, 21, 64
Submitted by Jonathan W. Williams and John A. Krynitsky.
Checked by Nathan L. Drake and Joseph Lann.
Three 300-ml. gas-washing cylinders (Note 1) are connected in series, and the second and third cylinders are charged with 150 ml. each of dry acetone. Each of the three cylinders is immersed, in a thermos bottle, in sufficient Dry Ice-acetone cooling mixture to cover half of the cylinder. Ketene gas, prepared by the pyrolysis of acetone (Note 2), is passed through the system (Note 3) until a quantity of 2 moles has been introduced. This process requires 4–4.5 hours. During this time, after the ketene has been passing through the system for 1.5 hours, the Dry Ice-acetone cooling mixture is removed from the thermos bottle around the first cylinder. The cold thermos bottle is then replaced around the cylinder. Two hours after the completion of the ketene passage, the cooling mixture is removed from the second thermos bottle, and 6 hours later the third thermos bottle is emptied, both bottles being immediately restored to position. The entire system should be at room temperature 24 hours after the beginning of the run.
The liquids from all three cylinders are combined and fractionally distilled (Note 4). Most of the acetone is removed at room temperature under a pressure of 20 mm.; the last small portion is removed under atmospheric pressure. When the distillation temperature reaches 120°, the system is evacuated to a pressure of 80–100 mm. (Note 5), and the ketene dimer is collected within the boiling range 67–69°/92 mm. The yield of pure product is 42–46 g. (50–55%) (Note 6) and (Note 7).
The gas-washing cylinders are preferably without flanges. Those used by the submitters were prepared from 45-mm. Pyrex tubing, measured 28 cm. in length, and were fitted with 29/42 standard taper ground-glass joints. The inlet tubes extended two-thirds of the way into the cylinders.
may be generated conveniently from acetone
by means of a "ketene
This apparatus was used by submitters and checkers. Other apparatus [Org. Syntheses Coll. Vol. 1, 331 (1941)]
might also be used.
The effluent gases from the third cylinder should be conducted to an efficient hood
, or passed through a washing bottle containing a 10% aqueous solution of sodium hydroxide
The submitters and checkers used a column of the Whitmore-Lux type
Pressure between these limits is the optimum for this distillation. At higher pressure too much polymerization to dehydroacetic acid
occurs, and at a lower pressure special cooling methods are necessary to prevent loss of distillate by evaporation.
A viscous dark red residue remains in the distillation flask. This material is mostly dehydroacetic acid
The Ketene dimer
may be kept in a tightly stoppered bottle
in the dark without appreciable further polymerization for about a week.2
The procedure described is a modification of the method of Chick and Wilsmore,3
which has been studied by several other workers.4 5 2
Homologous diketenes have been prepared by the action of tertiary amines on the corresponding acid chlorides.6
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
sodium hydroxide (1310-73-2)
Dehydroacetic acid (520-45-6)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved