B.
Cyclobutanone. A
2-l., three-necked flask is fitted with an
efficient mechanical stirrer and a
water-cooled condenser assembled for downward distillation to which is attached a
250-ml. receiver with a side arm. Two cold
traps are attached consecutively to the distillation apparatus as shown in
f.htmigure 2 (Note
12). The
receiver is immersed in an
ice-water bath, and the traps are immersed in dry ice and
acetone. To the flask is added
45 g. (0.28 mole) of 5,9-dithiaspiro[3.5]nonane,
900 ml. of triethylene glycol, and 150 ml. of water. Stirring is begun, and
163 g. (0.600 mole) of mercury(II) chloride (Note
13) and
51.5 g. (0.300 mole) of cadmium carbonate (Note
13) are added. A nitrogen-inlet tube reaching to the bottom of the flask is inserted into the third neck of the flask, and
nitrogen is introduced at approximately 50 ml. per minute. The reaction flask is heated to 90° in an
oil bath, and the temperature is slowly increased to 110° over a 2–3 hour period. Water and
cyclobutanone are carried into the receivers. The water in the receiving flask is saturated with
sodium chloride, and the resulting solution is transferred to a
separatory funnel. The flask is rinsed with
25 ml. of dichloromethane, and this solution is used for an initial washing of the aqueous solution. The aqueous solution is shaken three additional times with
25-ml. portions of 12chloromethane. The
dichloromethane solutions are combined and added to the traps to dissolve
cyclobutanone. The resulting solution is transferred to a
250-ml. flask, the traps are rinsed with a small amount of
dichloromethane, and the rinse is combined with the original solution. The organic solution is dried over
5 g. of anhydrous sodium sulfate, filtered, and the solvent is removed by distillation through a
20-cm., helix-packed, vacuum-insulated column. The product is transferred to a
25-ml. flask,
5 ml. of mesitylene is added, and the product is distilled through a spinning-band column. The fraction boiling at 95–100° is collected, yielding
12–15.8 g. (
60–81%) (Note
14) of
cyclobutanone.