Org. Synth. 1943, 23, 90
DOI: 10.15227/orgsyn.023.0090
TETRAHYDROPYRAN
[Pyran, tetrahydro-]
Submitted by D. W. Andrus and John R. Johnson.
Checked by Nathan L. Drake and Charles M. Eaker.
1. Procedure
The hydrogenation is carried out in a low-pressure catalytic hydrogenation apparatus.
Raney nickel catalyst
(p. 181) is washed with
ether three times on a
Büchner funnel, then 8 g. of it is transferred under
ether to the hydrogenation bottle. The bottle is fitted with a
rubber stopper bearing a
small dropping funnel and a glass tube that leads to one arm of a
three-way stopcock. The other arms of the stopcock are connected respectively to a
water pump and a source of inert gas
(Note 1) in such a way that the
ether can be pumped off and the bottle can then be filled with the inert gas. When this has been done,
50.5 g. (0.6 mole) of dihydropyran (p. 276) is introduced through the dropping funnel.
The bottle is connected to the hydrogenation apparatus and alternately evacuated and filled with hydrogen twice. Hydrogen is then admitted to the system until the pressure gauge reads 40 lb. The shaker is started, and the pressure drops to the theoretical value for absorption of 0.6 mole in 15–20 minutes; beyond this point shaking causes no further absorption of hydrogen (Note 2). The bottle is removed and the nickel catalyst is allowed to settle. The tetrahydropyran is decanted, but enough is left in the bottle to cover the catalyst (Note 3). The product boils at 85–86°, but it need not be distilled for many purposes. The yield is practically quantitative.
2. Notes
1.
Purified
nitrogen is a convenient inert gas, but natural gas containing no
oxygen, or
sulfur compounds, is equally suitable; the checkers used
hydrogen.
2.
As the catalyst becomes older, it loses its activity somewhat and a longer time is required for the pressure to drop to the theoretical value.
3.
The same catalyst may be used many times. For the next run the
dihydropyran is merely poured into the bottle containing the catalyst which is wet with the product of the previous run.
3. Discussion
Tetrahydropyran has been prepared by hydrogenation of
dihydropyran using a
platinum black catalyst;
1 by heating
pentamethylene bromide with water;
2,3 or with water and
zinc oxide in a
sealed tube;
4 or by heating
pentamethylene glycol with
3 volumes of 60% sulfuric acid in a
pressure tube,
5 or dehydration of this glycol in the vapor phase over
kaolin or aluminum oxide.
6
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
platinum black
kaolin
sulfuric acid (7664-93-9)
ether (60-29-7)
hydrogen (1333-74-0)
oxygen (7782-44-7)
nitrogen (7727-37-9)
sulfur (7704-34-9)
nickel,
Raney nickel (7440-02-0)
pentamethylene bromide (111-24-0)
pentamethylene glycol (111-29-5)
Tetrahydropyran,
Pyran, tetrahydro- (142-68-7)
zinc oxide
aluminum oxide (1344-28-1)
dihydropyran
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