Org. Synth. 1933, 13, 24
DOI: 10.15227/orgsyn.013.0024
BUTYROIN
[4-Octanone, 5-hydroxy-]
Submitted by John M. Snell and S. M. McElvain.
Checked by C. S. Marvel and M. R. Lehman.
1. Procedure
In a 3-l. three-necked, round-bottomed flask, fitted with a long reflux condenser and an efficient mechanical stirrer, are placed 92 g. (4 gram atoms) of clean metallic sodium and about 150 cc. of xylene. The sodium is finely powdered by heating the flask until the sodium melts and then cooling with very vigorous stirring. The cooled xylene is decanted, and the powdered sodium is thoroughly washed with four or five portions of dry, alcohol-free ether. About 1.2 l. of absolute ether is added (Note 1), and the flask is fitted with a reflux condenser, a 250-cc. separatory funnel, and a mechanical stirrer (Note 2).
The stirrer is started, and 232 g. (2 moles) of purified ethyl n-butyrate (Note 3) is slowly run in from the separatory funnel. It is advisable to add first a portion of about 25 cc.; the heat of reaction soon causes the ether to boil; the rest of the ester is then run in at such a rate that gentle ebullition is maintained. Stirring is continued until there is no further reaction and practically all the sodium has been converted into the voluminous yellow-white solid which begins to appear almost at once (Note 4).
The reaction flask is now surrounded by an ice bath, and the contents are vigorously stirred while a cooled solution of 210 g. of sulfuric acid (sp. gr. 1.84) in 350 cc. of water is carefully run in from the separatory funnel. The stirrer is now removed and the flask is allowed to stand in the ice bath until the lower layer of hydrated sodium sulfate (Na2SO4·10H2O) has solidified. The ether solution is decanted and the sodium sulfate crystals washed with 100–200 cc. of ether.
The combined solution and washings are shaken with about 100 cc. of 20 per cent sodium carbonate solution (Note 5) and are then dried over anhydrous potassium carbonate. The ether and alcohol are removed rapidly by distillation, and the residue is fractionated under reduced pressure in a 250-cc. modified Claisen flask (Note 6). The main fraction boils at 80–86° at 12 mm.; a fraction boiling up to about 15° above the main fraction should also be collected. The low-boiling and high-boiling fractions can be refractionated for recovery of a small additional amount of butyroin. The total yield is 94–101 g. (65–70 per cent of the theoretical amount) of product that is colored yellow by traces of the diketone (Note 7) and (Note 8).
2. Notes
1.
The reaction can be run in
benzene, but it is much slower than in
ether.
2.
For powdering the
sodium a small, rapid stirrer is best; for stirring the reaction mixture, a fairly large, slower stirrer is best.
3.
The ester is purified as follows: It is washed once with
10 per cent sodium carbonate solution and twice with an equal volume of saturated
sodium chloride solution; it is then dried twenty-four hours over anhydrous
potassium carbonate. The
potassium carbonate is filtered and the ester allowed to stand overnight with about
2 per cent of its weight of phosphorus pentoxide. The ester is then distilled through a
column directly from the
phosphorus pentoxide; a fraction that distils over a range of 2 degrees or less should be taken. Lower yields of
butyroin may be obtained from less carefully purified ester.
4.
Addition of the ester requires one and one-half to two hours, and the mixture should then be refluxed an hour longer.
5.
Small amounts of
butyric acid and
dipropylglycollic acid are present in the reaction mixture.
6.
The
ether should be removed rapidly and the distillation should not be too slow, for long heating favors the formation of a high-boiling by-product of unknown structure at the expense of the
butyroin.
7.
Usually the amount of diketone present is negligible. The diketone may be removed by shaking the
butyroin vigorously from time to time during one hour with
100 cc. of a saturated sodium bisulfite solution, washing with strong
sodium chloride solution, and then redistilling.
8.
These directions have been used for the following acyloins:
| Propionoin b.p. 60–65°/12 mm.; 50–55 per cent yield. |
| Isobutyroin b.p. 70–75°/14 mm.; 70–75 per cent yield. |
| Pivaloin m.p. 80–81°; b.p. 85–95°/12 mm.; 52–60 per cent yield |
3. Discussion
Aliphatic acyloins can be obtained by the saponification of the reaction product of
sodium on moist ethereal solutions of acid chlorides, the first product being the diester of the dienolic modification of the acyloin.
1 Of greater preparative interest, however, is the reaction between ethereal solutions of aliphatic esters and
sodium2 or
potassium.
3This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
potassium carbonate (584-08-7)
sulfuric acid (7664-93-9)
Benzene (71-43-2)
ether (60-29-7)
sodium chloride (7647-14-5)
sodium carbonate (497-19-8)
sodium sulfate (7757-82-6)
sodium bisulfite (7631-90-5)
sodium,
metallic sodium (13966-32-0)
butyric acid (107-92-6)
potassium (7440-09-7)
xylene (106-42-3)
Butyroin,
4-Octanone, 5-hydroxy- (496-77-5)
dipropylglycollic acid
Propionoin (4984-85-4)
Isobutyroin (815-77-0)
Pivaloin (815-66-7)
ethyl n-butyrate (105-54-4)
phosphorus pentoxide (1314-56-3)
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