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Org. Synth. 1930, 10, 84
DOI: 10.15227/orgsyn.010.0084
l-PROPYLENE GLYCOL
[1,2-Propanediol, l-]
Submitted by P. A. Levene and A. Walti.
Checked by Frank C. Whitmore and J. Pauline Hollingshead.
1. Procedure
A solution of 1 kg. of sucrose in 9 l. of water is placed in a 20-l. bottle provided with a gas trap. A paste of baker's yeast (Note 1) is made by breaking up 1 kg. of yeast and gradually stirring in 1 l. of water. This is then added to the sugar solution and the mixture is allowed to stand at room temperature until a lively evolution of gas starts (from one to three hours). To the vigorously fermenting solution 100 g. (1.35 moles) of freshly prepared acetol (p. 5) is added, and the mixture is allowed to stand at room temperature until the reaction subsides (Note 2). The bottle is then transferred to an incubator at 32°, when the fermentation recommences. At the end of three days the reaction is generally completed, and the solution when tested with Fehling's reagent gives a negligible test for reducing sugars.
At this point 20–30 g. of short glass fiber or asbestos is added and the yeast is filtered by suction. The filtrate is concentrated to a thick syrup under diminished pressure on a water bath, the temperature being kept below 40° (Note 3). The residue (about 200 cc.) is taken up in a mixture of 400 cc. of absolute alcohol and 100 cc. of dry ether (Note 4). The precipitate formed is removed by centrifuging, the supernatant liquid is decanted, and the residue is extracted with a mixture of 200 cc. of 98.5 per cent alcohol and 100 cc. of dry ether (Note 5). The combined alcohol-ether solutions are concentrated under diminished pressure at 35–40° to a thick syrup. The residue is again taken up in a mixture of 400 cc. of 98.5 per cent alcohol and 100 cc. of dry ether and centrifuged (Note 5). The supernatant liquid is concentrated under diminished pressure and distilled from a modified Claisen flask. The yield of the crude product boiling at 86–91°/12 mm. is approximately 100 g. The crude material is refractionated and collected at 88–90°/12 mm. or 187–189°/760 mm. The final product (Note 4) is a colorless liquid having a density 1.04 and specific rotation [α]20D = −15.0°. The yield is 50–60 g. (49–58 per cent of the theoretical amount) (Note 6).
2. Notes
1. Fleischmann's yeast is satisfactory.
2. The addition of the acetol may cause the reaction to slacken for a time.
3. The evaporation must be carried out at as low a temperature as is practicable. A suitable device for this evaporation is given in Org. Syn. Coll. Vol. I, 1941, 427.
4. The product reacts slightly acid. If an entirely neutral l-propylene glycol is desired, the syrup first obtained should be made neutral with a solution of sodium methoxide in methyl alcohol, and again concentrated and extracted as indicated.
5. If a centrifuge is not available the same result may be obtained by adding about 15 g. of short glass fiber or asbestos to the solution, stirring the solution mechanically or shaking it vigorously for five minutes, and filtering with suction.
6. The optically active glycols are convenient starting materials for the preparation of optically active carbinols, hydroxyacids, etc. The biological method of asymmetric reduction is perhaps the only convenient method for the preparation of these glycols. The steps in the preparation of other optically active glycols are identical with those in the preparation of l-propylene glycol from acetone. In the synthesis of certain glycols it is convenient to prepare the chloroketone by oxidizing the corresponding chlorohydrin, the succeeding steps being the same as those in the synthesis of l-propylene glycol.
3. Discussion
l-Propylene glycol has been obtained from the optically inactive glycol by the action of bacteria,1 and by means of strychnine compounds.2 The present method is based on that of Färber, Nord, and Neuberg.3

References and Notes
  1. LeBel, Jahresb. 1881, 512.
  2. Grün, Ber. 52, 260 (1919).
  3. Färber, Nord, and Neuberg, Biochem. Z. 112, 313 (1920).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

Fehling's reagent

glycol

alcohol (64-17-5)

Acetol (64-19-7)

methyl alcohol (67-56-1)

ether (60-29-7)

sucrose

acetone (67-64-1)

sodium methoxide (124-41-4)

L-Propylene glycol,
1,2-Propanediol, l- (57-55-6)