Org. Synth. 1930, 10, 12
BROMOACETONE
[2-Propanone, 1-bromo-]
Submitted by P. A. Levene
Checked by Frank C. Whitmore and J. Pauline Hollingshead.
1. Procedure
A 5-l., three-necked, round-bottomed flask is provided with an efficient mechanical stirrer, a 48-cm. Allihn reflux condenser, a thermometer, and a 500-cc. separatory funnel, the stem of which reaches nearly to the bottom of the flask (Note 1).
Through the separatory funnel are introduced 1.6 l. of water,
500 cc. of c. p. acetone, and
372 cc. of glacial acetic acid. The stirrer is started and the temperature of the
water bath is raised to 70–80°, so that the mixture in the flask is at about 65°
(Note 2). Then
354 cc. (7.3 moles) of bromine is carefully added through the separatory funnel. The addition, which requires one to two hours, is so regulated as to prevent the accumulation of unreacted
bromine (Note 3). As a rule the solution is decolorized in about twenty minutes after the
bromine has been added. When the solution is decolorized, it is diluted with 800 cc. of cold water, cooled to 10°, made neutral to
Congo red with about
1 kg. of solid anhydrous sodium carbonate, and the oil which separates is collected in a separatory funnel and dried with
80 g. of anhydrous calcium chloride. After drying, the oil is fractionated and the fraction boiling at
38–48°/13 mm. is collected. The yield is
470–480 g. (
50–51 per cent of the theoretical amount). It may be used without further purification for the preparation of
acetol (p. 5); but, if a purer product is desired, the above product is refractionated and the fraction boiling at
40–42°/13 mm. is collected. The yield is
400–410 g. (
43–44 per cent of the theoretical amount).
The higher-boiling fraction contains a mixture of isomeric dibromoacetones.
2. Notes
1.
The apparatus should be set up with the flask in a
large container (such as a
14-qt. galvanized pail) to be used as a water bath, and under a
well-ventilated hood, as both the
bromine and
bromoacetone are powerful irritants to the skin and mucous membranes.
2.
It is necessary to warm the reaction mixture to this temperature to ensure a smooth reaction
3.
It is not advisable to have too great an excess of
bromine present at any time, as it sometimes reacts suddenly with great violence.
3. Discussion
Bromoacetone has been prepared by the electrolysis of a mixture of
acetone and
hydrobromic acid,
1 and by more orthodox methods of bromination: the addition of
bromine to
acetone dissolved in ten times its weight of water;
2 the addition of
bromine to
acetone in which marble is suspended;
3 the addition of
bromine to
acetone, water, and concentrated
hydrochloric acid;
4 and the introduction of
bromine by means of a current of air into cold
acetone.
5
A procedure similar to the one described above, except that the reaction mixture is illuminated with a powerful light, has been published.
6This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
Congo red
dibromoacetones
calcium chloride (10043-52-4)
hydrochloric acid (7647-01-0)
acetic acid,
Acetol (64-19-7)
HYDROBROMIC ACID (10035-10-6)
sodium carbonate (497-19-8)
bromine (7726-95-6)
acetone (67-64-1)
Bromoacetone,
2-Propanone, 1-bromo- (598-31-2)
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