Organic Syntheses, CV 2, 5
Submitted by P. A. Levene and A. Walti.
Checked by Frank C. Whitmore and J. Pauline Hollingshead.
1. Procedure
In a
3-l. round-bottomed flask fitted with a
75-cm. Liebig condenser is placed
210 g. of potassium hydroxide (purified with alcohol) dissolved in
1.5 l. of anhydrous methyl alcohol. The solution is cooled to below 50° (Note
1),
300 g. of purified ethyl formate is added, and the mixture is refluxed for two hours (Note
2) and (Note
3).
Then
410 g. (251 cc., 3 moles) of bromoacetone (p. 88) is added, and the mixture is refluxed for sixteen hours on a
water bath at 95–97°. At the end of the operation the solution is cooled to 0° in an
ice-salt bath. The
potassium bromide which settles is filtered on a cooled
suction filter, and the filtrate is fractionated.
The fraction boiling at 23–35°/12 mm. is discarded, as it contains very little
acetol. The main fraction distils at
35–47°/12 mm. and weighs
160 g. This material is refractionated, and the portion boiling at
40–43°/12 mm. is collected. The yield is
120–130 g. (
54–58 per cent of the theoretical amount) (Note
4).
2. Notes
1. It is necessary to cool the mixture below 50° to prevent loss of the volatile
ethyl formate.
2. Technical
ethyl formate was purified by washing with
3 per cent sodium carbonate solution, then with cold water, drying over anhydrous
sodium sulfate, filtering, and fractionating. Compare
p. 180. It is very important that all the materials used in the synthesis of
acetol be anhydrous, as otherwise condensation products are formed.
3. If commercial
potassium formate is used it should be dried under reduced pressure at 80°. One and one-half to two moles should be used per mole of the bromo compound.
4.
Acetol polymerizes very readily on standing but remains unchanged when dissolved in an equal volume of
methyl alcohol.
3. Discussion
This preparation is referenced from:
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