Org. Synth. 1925, 5, 33
DOI: 10.15227/orgsyn.005.0033
CYCLOHEXENE
Submitted by G. H. Coleman and H. F. Johnstone.
Checked by C. S. Marvel and A. B. Adams.
1. Procedure
In a
500-cc. modified Claisen flask (p. 130) are placed
400 g. (4 moles) of cyclohexanol (Note 1) and
12 cc. of concentrated sulfuric acid, and the flask is connected to a
condenser and
receiver surrounded by an
ice bath. It is then placed in an
oil bath which is heated to a temperature of 130–140°. The distillation is continued until only a small residue remains and the odor of
sulfur dioxide is apparent. Toward the end of the distillation the temperature of the bath may be raised to 150°. The receiver is kept cold
(Note 2) during the entire distillation, which requires from five to six hours
(Note 3).
The distillate is saturated with salt, and the cyclohexene is separated from the water layer. It is dried with calcium chloride and fractionated through an efficient column (Note 4). The fraction boiling at 80–82° (uncorr.) is collected separately. It may be necessary to refractionate the low- and high-boiling portions once or twice (Note 5). The high-boiling fraction is finally added to the next run. The yield of cyclohexene is 260–285 g. (79–87 per cent of the theoretical amount) (Note 6).
2. Notes
1.
The ordinary commercial grade of
cyclohexanol was used in these experiments. It contained no more than a trace of
phenol, and 90–95 per cent of it distilled at 158–163°.
2.
In transferring
cyclohexene, it is best to keep it well cooled to avoid small losses by evaporation.
3.
The time required for this distillation can be reduced to about two hours by boiling the mixture in a
round-bottomed flask provided with a
reflux condenser with water maintained at about 75°. A tube at the top of the reflux condenser leads to a
downward cold-water condenser.
14.
The
partial condenser illustrated in Org. Syn.
20, 27, which is a modification of an apparatus described by Hahn,
2 is very efficient in the purification of
cyclohexene (A. W. Hutchison, private communication).
5.
It has been suggested that the crude fraction be refluxed with
sodium to remove
cyclohexanol prior to a final fractionation.
36.
For the preparation of
cyclohexene in large quantity, distillation of
cyclohexanol over
silica gel4 or, better, activated
alumina is more rapid and efficient. Using a
25-mm. tube packed with 8- to 14- mesh activated alumina (Aluminum Company of America) and heated to 380–450° over a 30-cm. length,
1683 g. of cyclohexanol was dehydrated in about four hours. After separating the water, drying with
sodium sulfate, and fractionating with a
simple column,
1222 g. (
89 per cent yield) of
cyclohexene, b.p.
82–84°, was obtained. (E. B. Hershberg and John R. Ruhoff, private communication, and Org. Syn.
17, 27.)
3. Discussion
Cyclohexene can be prepared from
cyclohexanol by dehydration with
potassium bisulfate,
5 oxalic acid,
6 sulfuric acid,
7 p-toluenesulfonic acid,
8 phosphoric acid,
9 iodine,
10 and at elevated temperatures over various catalysts.
4,
11 Cyclohexene has also been prepared from
cyclohexyl chloride by passage with steam over
activated carbon at 260–300°,
12 and from
benzene by treatment with the substance
Ca(NH3)6.
13 The procedure described is a slight modification of that described by Senderens
7 and later modified by Osterberg and Kendall.
7
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
alumina
silica gel
Ca(NH3)6
calcium chloride (10043-52-4)
sulfuric acid (7664-93-9)
Benzene (71-43-2)
Cyclohexanol (108-93-0)
phenol (108-95-2)
Cyclohexene (110-83-8)
sulfur dioxide (7446-09-5)
sodium sulfate (7757-82-6)
Oxalic acid (144-62-7)
potassium bisulfate (7646-93-7)
iodine (7553-56-2)
activated carbon (7782-42-5)
sodium (13966-32-0)
phosphoric acid (7664-38-2)
cyclohexyl chloride (542-18-7)
p-toluenesulfonic acid (104-15-4)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved