Org. Synth. 1932, 12, 48
DOI: 10.15227/orgsyn.012.0048
METHYL ISOPROPYL CARBINOL
[2-Butanol, 3-methyl-]
Submitted by Nathan L. Drake and Giles B. Cooke.
Checked by C. S. Marvel and B. H. Wojcik.
1. Procedure
In a 3-l. three-necked flask, fitted with a mechanical stirrer, a separatory funnel, and a reflux condenser the upper end of which is protected by a calcium chloride tube, are placed 146 g. (6 gram atoms) of dry magnesium turnings (Note 1) and about 250 cc. of dry ether (Note 2).
A solution of 600 g. (4.9 moles) of isopropyl bromide (Note 3) in 300 cc. of dry ether is then added through the separatory funnel. The reaction begins after about 15 cc. of the solution has been added (Note 4). The solution is added at such a rate that the reaction mixture refluxes gently. It is well to arrange to cool the flask with running water if the refluxing becomes too vigorous. The addition of the isopropyl bromide solution should require from three and one-half to four hours. The reaction mixture is refluxed on the water bath for forty minutes after addition of the isopropyl bromide solution is complete.
The flask is then cooled to −5° (Note 5), and a solution of 200 g. (4.5 moles) of acetaldehyde (Note 6) in 250 cc. of dry ether is added at this temperature over a period of one hour.
After addition of the acetaldehyde solution is complete, the product is decomposed by pouring the reaction mixture onto 2 kg. of cracked ice. The excess magnesium may be removed conveniently by decantation at this point. The basic magnesium halide is dissolved by addition of about 1 l. of 15 per cent sulfuric acid. The ether solution is separated, and the aqueous layer is extracted with four 150-cc. portions of ether. The ether solutions are combined, dried over 25 g. of calcined potassium carbonate, filtered, and fractionally distilled, using a short column. The methyl isopropyl carbinol distils at 110–111.5°. The fraction boiling at 37–109° should be dried and refractionated. The total yield is 210–215 g. (53–54 per cent of the theoretical amount).
2. Notes
1.
The excess of
magnesium is used to increase the yield of Grignard reagent.
2.
More
ether may be added during the preparation to replace any which may be lost. The
ether used should be dried over bright
sodium wire.
3.
The
isopropyl bromide (b.p.
59–60°) was obtained from the Eastman Kodak Company and was used without further treatment. Directions for preparing
isopropyl bromide are given in
Org. Syn. Coll. Vol. I, 1941, 37, and on
p. 359 above.
4.
Heating on the water bath to start the reaction should be unnecessary if all the apparatus and reagents are completely dry.
5.
The temperature must not be allowed to rise above −5°.
6.
The
acetaldehyde may be prepared conveniently by depolymerizing pure, dry
paraldehyde with
toluenesulfonic acid as a catalyst.
Acetaldehyde boiling at
20.5–21° must be used for this preparation. There is no advantage in using gaseous
acetaldehyde.
3. Discussion
Methyl isopropyl carbinol has been prepared by reduction of
methyl isopropyl ketone with
sodium amalgam,
1 and with
sodium;
2 by treatment of
chloroacetyl chloride with
zinc methyl;
3 by treatment of
bromoacetyl bromide with
zinc methyl;
4 by treatment of
isobutyraldehyde with
methylmagnesium bromide;
5 and as a by-product of the reaction between
chloroacetone and
methylmagnesium iodide.
6
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
zinc methyl
acetaldehyde (75-07-0)
potassium carbonate (584-08-7)
sulfuric acid (7664-93-9)
ether (60-29-7)
magnesium,
magnesium turnings (7439-95-4)
Isopropyl bromide (75-26-3)
sodium,
sodium wire (13966-32-0)
chloroacetyl chloride (79-04-9)
methylmagnesium iodide (917-64-6)
bromoacetyl bromide (598-21-0)
chloroacetone (78-95-5)
Methyl isopropyl carbinol,
2-Butanol, 3-methyl- (598-75-4)
toluenesulfonic acid (88-20-0)
Methyl isopropyl ketone (563-80-4)
isobutyraldehyde (78-84-2)
methylmagnesium bromide (75-16-1)
paraldehyde (123-53-7)
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