Organic Syntheses, CV 1, 192
Submitted by J. F. Thorpe and G. A. R. Kon.
Checked by Roger Adams and C. R. Noller.
1. Procedure
In a
1-l. distilling flask (Note
1), fitted with a
thermometer reaching within 5 mm. of the bottom, is placed an intimate mixture of
200 g. (1.34 moles) of powdered adipic acid (Note
2) and
10 g. of finely ground crystallized barium hydroxide. The mixture is gradually heated in a
fusible alloy bath (Note
3) to 285–295° (Note
4) during about one and one-half hours, and maintained at that temperature until only a small amount of dry residue remains in the flask. This requires about two hours longer. The
cyclopentanone distils slowly, accompanied by small quantities of
adipic acid.
The ketone is separated from the water in the distillate, either by salting out with
calcium chloride or by extracting with a little
ether (Note
5). It is washed with a little aqueous alkali and then with water, dried over
calcium chloride, and distilled through a good
fractionating column (Note
6). The fraction boiling at
128–131° is
cyclopentanone. The yield is
86–92 g. (
75–80 per cent of the theoretical amount).
2. Notes
1. If larger runs are made, a
three-necked flask provided with a
mechanical stirrer should be used for the reaction.
2. The unrecrystallized
adipic acid, prepared as described on
p. 18, may be used.
3. An
air bath may be used, but the
metal bath insures better temperature control.
4. If the temperature goes above 300°, the
adipic acid begins to distil quite rapidly. It is best to hold the temperature as near 290° as is possible.
6.
Cyclopentanone is quite volatile with
ether vapor, and careful fractionation is necessary when
ether is used for the separation of the ketone from the water.
3. Discussion
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