Org. Synth. 1933, 13, 68
DOI: 10.15227/orgsyn.013.0068
METHYL ISOPROPYL KETONE
[2-Butanone, 3-methyl-]
Submitted by Frank C. Whitmore, W. L. Evers, and H. S. Rothrock.
Checked by W. W. Hartman and L. J. Roll.
1. Procedure
In a 1.5-l. round-bottomed Pyrex flask, fitted with a dropping funnel, an efficient mechanical stirrer, and a thermometer, is placed 176 g. (2 moles) of tert.-amyl alcohol (redistilled, b.p. range 0.5°). The flask is surrounded by a water bath, and the temperature of the alcohol is held at 50–60° while 320 g. (103 cc., 2 moles) of bromine is slowly added with stirring during about two hours (Note 1). The stirring is continued for a few minutes until the bromine color has disappeared (Note 2).
To the reaction flask containing the crude trimethylethylene dibromide is added 540 cc. of water, and the flask is fitted with a long reflux condenser and a mercury-sealed stirrer (Note 3). The mixture is refluxed with stirring for three to five hours until hydrolysis is practically complete (Note 4). The reflux condenser is then replaced by a condenser for distillation, and the crude methyl isopropyl ketone is removed from the reaction mixture by direct distillation, with stirring, until the temperature rises (Note 5) and the oil nearly stops coming over (about one and one-half hours), or until the oil coming over is heavier than water. The residue in the flask can be distilled to yield about 380 cc. of constant-boiling hydrobromic acid.
To the distillate, consisting of a yellow oil with a small lower water layer, powdered sodium carbonate (about 10 g.) is added, and the mixture is shaken until the water layer is alkaline and nearly saturated (Note 6). The layers are separated, and the oil is refluxed for about sixteen hours with 20 g. of powdered potassium carbonate and 5 cc. of water (Note 7). The oily layer is again separated and dried over about 6 g. of anhydrous calcium chloride or potassium carbonate (Note 8). It is then placed in a flask containing 2 g. of dry sodium carbonate and distilled through an efficient column. The yield of methyl isopropyl ketone boiling at 92–94° (Note 9) is about 102 g. (59 per cent of the theoretical amount). The product is slightly yellow.
2. Notes
1.
The
bromine is added at such a rate that only a small amount is present at any time, as shown by an orange-red color. The speed of the reaction depends on the temperature and efficiency of stirring. The temperature of the reaction mixture remains a few degrees above that of the water bath.
After about half the bromine has been added, the mixture becomes cloudy owing to the separation of water, and a somewhat lower temperature (40–45°) suffices to prevent the accumulation of unreacted bromine.
2.
The crude
trimethylethylene dibromide can be purified by washing with
sodium carbonate solution and water, drying, and distilling under reduced pressure; b.p.
49–51°/11 mm.;
60–70 per cent yield. Hydrolysis of the purified dibromide gives a
78 per cent yield of
methyl isopropyl ketone. However, the losses in purifying the dibromide result in a slightly decreased over-all yield of ketone so that the purification of the dibromide is not recommended.
3.
The quantity of water used is 50 per cent more than the theoretical amount for hydrolyzing the dibromide and converting all the
bromine to constant-boiling
(47.3 per cent) hydrobromic acid. Less water can be used, but more darkening of the reaction mixture occurs, and the yield of ketone is slightly decreased.
4.
Efficient stirring lessens the time required for hydrolysis and avoids loss of material by intermittent sudden boiling. To be sure of complete hydrolysis, refluxing should be continued for at least an hour after the specific gravity of the oily layer becomes less than that of the water layer.
5.
The distillate and residue contain a very powerful lachrymator and should be handled under a good
hood.
6.
The ketone is somewhat soluble in water, and the
sodium carbonate serves to salt it out as well as to remove any
hydrobromic acid.
7.
The crude ketone contains small amounts of bromides, and it darkens even after repeated distillation unless first refluxed over
potassium carbonate.
8.
It is necessary to dry the ketone thoroughly since water distils with it at about 78°. This fraction can be dried again to recover the ketone.
9.
A
column 55 cm. high packed with glass tubes 6 mm. in length and diameter was employed with good results. A few grams of
trimethylethylene, b.p.
34–36°/735 mm., is always obtained if adequate condensers have been used throughout the preparation. The presence of a little
sodium carbonate during the final distillation hinders decomposition.
3. Discussion
Trimethylethylene dibromide has been obtained by the reaction between
bromine and
trimethylethylene1 or
tertiary amyl alcohol.
2
Methyl isopropyl ketone has been obtained by the hydration of
isopropylacetylene;
3 from
isopropylmagnesium bromide and
acetic anhydride;
4 from
isopropylmagnesium chloride and
ethyl acetate;
5 by the hydrolysis of
ethyl dimethylacetoacetate;
6 by passing a mixture of the vapors of
isobutyric and acetic acids over a
thoria catalyst;
7 and from
butane or isobutane,
aluminum chloride, and
carbon monoxide.
8 Methyl isopropyl ketone can also be obtained by rearrangement of
methyl isopropenyl carbinol9 or
trimethylethylene oxide;
10 by heating
trimethylethylene glycol with dilute
hydrochloric acid;
11 by heating
trimethylethylene chlorohydrin (2-methyl-2-hydroxy-3-chlorobutane) with water;
12 and by the hydrolysis of
trimethylethylene dibromide.
13
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
thoria
isobutyric and acetic acids
calcium chloride (10043-52-4)
potassium carbonate (584-08-7)
hydrochloric acid (7647-01-0)
ethyl acetate (141-78-6)
acetic anhydride (108-24-7)
carbon monoxide (630-08-0)
HYDROBROMIC ACID (10035-10-6)
sodium carbonate (497-19-8)
bromine (7726-95-6)
aluminum chloride (3495-54-3)
Methyl isopropyl ketone,
2-Butanone, 3-methyl- (563-80-4)
Trimethylethylene dibromide (594-51-4)
trimethylethylene (513-35-9)
tertiary amyl alcohol,
tert.-amyl alcohol (75-85-4)
isopropylacetylene (598-23-2)
isopropylmagnesium bromide (920-39-8)
isopropylmagnesium chloride (1068-55-9)
ethyl dimethylacetoacetate
butane (106-97-8)
methyl isopropenyl carbinol (10473-14-0)
trimethylethylene oxide
trimethylethylene glycol (7778-85-0)
trimethylethylene chlorohydrin
2-methyl-2-hydroxy-3-chlorobutane
isobutane (75-28-5)
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