Org. Synth. 1943, 23, 67
DOI: 10.15227/orgsyn.023.0067
PENTAMETHYLENE BROMIDE
[Pentane, 1,5-dibromo-]
Submitted by D. W. Andrus
Checked by Nathan L. Drake and Charles M. Eaker.
1. Procedure
A
hydrobromic acid solution
[Org. Syntheses Coll. Vol. 1, 26 (1941)] is prepared in a
500-ml. round-bottomed flask by passing
sulfur dioxide into a mixture of
120 g. (37.7 ml., 0.75 mole) of bromine, 50 ml. of water, and 150 g. of crushed ice. This is equivalent to a mixture of
253 g. (1.5 moles) of 48% hydrobromic acid and
74 g. of concentrated sulfuric acid. To the mixture
21.5 g. (0.25 mole) of tetrahydropyran (p. 794) is added, a
reflux condenser is attached to the flask, and the light-brown homogeneous mixture is refluxed for 3 hours
(Note 1).
The heavy lower layer is separated (Note 2), washed once with a saturated solution of sodium bicarbonate and once with water, and then dried over 4–5 g. of anhydrous calcium chloride. The crude product is decanted from the calcium chloride, and the drying agent is rinsed once or twice with a small quantity of ethyl bromide which is added to the main product. The mixture is distilled under reduced pressure, and the pentamethylene bromide, which weighs 46–47 g. (80–82%), is collected at 104–106°/19 mm.
2. Notes
1.
The submitter refluxed the mixture for 10 hours, but the checkers obtained equally good yields in 3 hours.
2.
The upper aqueous layer contains considerable unchanged
hydrobromic acid. If this layer is distilled, about
150 g. (0.9 mole) of constant-boiling hydrobromic acid (b.p.
123–124°/748 mm.) may be recovered.
3. Discussion
The methods of preparing
pentamethylene bromide are given in
Org. Syntheses Coll. Vol. 1, 428 (1941), where the preparation of the dihalide from
benzoylpiperidine and
phosphorus pentabromide is described in detail. The procedure given above is based upon the work of Paul.
1
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
calcium chloride (10043-52-4)
sulfuric acid (7664-93-9)
sodium bicarbonate (144-55-8)
HYDROBROMIC ACID (10035-10-6)
bromine (7726-95-6)
sulfur dioxide (7446-09-5)
Ethyl bromide (74-96-4)
Benzoylpiperidine (776-75-0)
pentamethylene bromide,
Pentane, 1,5-dibromo- (111-24-0)
Tetrahydropyran (142-68-7)
phosphorus pentabromide (7789-69-7)
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