Org. Synth. 1951, 31, 66
DOI: 10.15227/orgsyn.031.0066
IODOCYCLOHEXANE
[Cyclohexane, iodo-]
Submitted by Herman Stone and Harold Shechter
1.
Checked by T. L. Cairns and V. A. Engelhardt.
1. Procedure
Forty-one grams (0.5 mole) of cyclohexene (Note 1) is added to a mixture of 250 g. (1.5 moles) of potassium iodide in 221 g. (2.14 moles) of 95% orthophosphoric acid (Note 2), (Note 3), and (Note 4) contained in a 1-l. three-necked flask equipped with a reflux condenser, a sealed mechanical stirrer, and a thermometer. The mixture is stirred and heated at 80° for 3 hours, after which it is allowed to cool and treated with 150 ml. of water and 250 ml. of ether with continued stirring (Note 5) and (Note 6). The ether extract is separated, decolorized with 50 ml. of 10% aqueous sodium thiosulfate solution, washed with 50 ml. of saturated sodium chloride solution, and dried with anhydrous sodium sulfate (50 g.). The ether is evaporated on a steam bath, and the product is distilled from a modified Claisen flask under reduced pressure. The portion boiling at 48–49.5°/4 mm. is collected. The yield of iodocyclohexane is 93–95 g. (88–90%), nD20 1.551, d420 1.625.
2. Notes
1.
Cyclohexene was obtained from Eastman Kodak Company.
2.
The
95% orthophosphoric acid is prepared by adding
174 g. (102 ml., 1.5 moles) of 85% phosphoric acid with stirring to
47 g. of phosphoric anhydride. The solution should be cooled to room temperature before the addition of
potassium iodide; otherwise evolution of
hydrogen iodide and formation of
iodine will take place. After the
cyclohexene has been added, the mixture can be heated as desired, since the
hydrogen iodide reacts as rapidly as it is generated.
3.
Although
95% orthophosphoric acid is recommended for this method,
commercial phosphoric acid (85%) may be used, but the reaction proceeds more slowly and the yield is lower.
4.
This procedure has been used for the conversion of other olefins to iodides in excellent yield. Yields of
2-iodohexane and
2,3-dimethyl-2-iodobutane from
1-hexene and
2,3-dimethyl-2-butene were 94.5 and 91.4%, respectively.
5.
Excess
potassium iodide can be recovered by filtering the acid layer, after adding sufficient water to dissolve precipitated inorganic phosphates.
6.
If the acid layer has an
iodine color, another extraction with
100 ml. of ether is recommended.
3. Discussion
Iodocyclohexane has been prepared by the action of
phosphorus and
iodine on
cyclohexanol,
2 and from
hydrogen iodide and
cyclohexanol,
3 chlorocyclohexane,
4 or
cyclohexyl ether.
5 It has also been prepared by reaction of
potassium iodide and
chlorocyclohexane,
6 by the reaction of
iodine with
cyclohexyldiphenyl phosphite,
7 and by the condensation of
triphenyl phosphite,
methyl iodide, and
cyclohexanol.
8
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ether (60-29-7)
Cyclohexanol (108-93-0)
Cyclohexene (110-83-8)
sodium chloride (7647-14-5)
PHOSPHORUS (7723-14-0)
sodium sulfate (7757-82-6)
potassium iodide (7681-11-0)
sodium thiosulfate (7772-98-7)
iodine (7553-56-2)
phosphoric acid,
orthophosphoric acid (7664-38-2)
hydrogen iodide (10034-85-2)
chlorocyclohexane (542-18-7)
Methyl iodide (74-88-4)
2,3-dimethyl-2-butene (563-79-1)
phosphoric anhydride (2466-09-3)
1-hexene (592-41-6)
Iodocyclohexane,
Cyclohexane, iodo- (626-62-0)
2-iodohexane
2,3-dimethyl-2-iodobutane
cyclohexyl ether
cyclohexyldiphenyl phosphite
triphenyl phosphite (101-02-0)
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