Org. Synth. 1960, 40, 76
DOI: 10.15227/orgsyn.040.0076
NEOPENTYL ALCOHOL
[2,2-Dimethyl-1-propanol]
Submitted by Joseph Hoffman
1
Checked by John D. Roberts and J. Eric Nordlander.
1. Procedure
A. Preparation of hydroperoxide. In a 2-l. three-necked round-bottomed flask, equipped with a mechanical stirrer (Note 1), a dropping funnel, and a thermometer, is placed 800 g. of 30% hydrogen peroxide (Note 2). The flask is surrounded by an ice bath and rapid stirring is started. In the meantime, 800 g. of 95–96% sulfuric acid is added to 310 g. of cracked ice and the solution is cooled to 10°. When the temperature of the hydrogen peroxide reaches 5–10°, the cold sulfuric acid is added slowly from the dropping funnel during a period of about 20 minutes (Note 3). The temperature of the solution should not exceed 20° during the addition. Commercial diisobutylene (224.4 g., 2 moles) is now added over a period of 5–10 minutes. The ice bath is removed and replaced by a water bath maintained at approximately 25° (Note 4). Vigorous agitation is maintained for 24 hours (Note 5). At the end of this time, mixing is discontinued, the mixture is transferred to a 2-l. separatory funnel and the two layers are allowed to separate (Note 6).
B. Decomposition of hydroperoxide. The upper organic layer (240–250 g.) is removed (Note 7) and added with vigorous stirring to 500 g. of 70% sulfuric acid in a 1-l. three-necked round-bottomed flask fitted with thermometer, stirrer, and dropping funnel and surrounded by an ice bath. The reaction temperature is maintained at 15–25° during addition, which requires 65–75 minutes (Note 8). Stirring is continued for 30 minutes at 5–10°, and then the reaction mixture is allowed to stand (0.5–3 hours) until the two layers are completely separated. The mixture is now transferred to a 1-l. separatory funnel and allowed to stand for about 15 minutes, after which time the lower layer is drawn off into 1 l. of water. The resulting mixture is distilled from a 3-l. flask without fractionation. The distillation is complete when 50–100 ml. of water has been collected (Note 9). The upper organic layer from the distillate (180–190 g.) is removed and dried over anhydrous magnesium sulfate (Note 10). The dried organic layer is filtered with the aid of a small amount of ether and distilled through an efficient fractionating column. The fraction which boils at 111–113° is collected (Note 11) and (Note 12). The yield is 60–70 g. (34–40% of theory, based upon the diisobutylene).
2. Notes
1.
A heavy nichrome wire twisted into 4 loops (similar to an egg beater) was found to be very satisfactory. The two ends of the wire, extending several inches beyond the loops, were pushed into a piece of glass tubing for the stirrer shaft.
2.
If the
hydrogen peroxide is slightly below 30%, enough should be used to give the amount called for. The acid concentration should be maintained by increasing the
sulfuric acid proportionately.
3.
The
hydrogen peroxide-sulfuric acid solution consists of approximately 12.5% hydrogen peroxide and 40% sulfuric acid.
4.
Good results have been obtained in the temperature range 23–27°. Although the heat given off during the reaction is not great and is spread over a long period of time, the reaction vessel must nevertheless be surrounded by a
water bath. If the room temperature is in the range indicated, no further regulation of the water bath temperature is required.
5.
It is necessary to provide rapid and vigorous stirring in order to obtain good results.
6.
The aqueous layer now contains approximately
8% hydrogen peroxide. This layer may be reused by adjusting the
hydrogen peroxide percentage to 12.5 by use of either
30% or 50% hydrogen peroxide. The
sulfuric acid must be readjusted to 40%. Approximately 1.9 kg. of aqueous layer is required for
2 moles of diisobutylene.
7.
The submitter states that the procedure may be interrupted at this point by washing the organic layer free of acid with a saturated solution of
sodium bicarbonate and that the
hydroperoxide concentrate will keep for a long time, especially if refrigerated.
8.
Care should be taken in decomposing the
hydroperoxide. If the temperature is kept too low, decomposition takes place too slowly and
hydroperoxide may accumulate. Heat is liberated during the decomposition, and after each small addition the temperature will rise. At the start, small amounts of
hydroperoxide are added until the temperature rises above 15°; the rate is then adjusted to keep the temperature in the range 15–25°. The rise in temperature after each small addition is the best evidence that decomposition is actually taking place.
9.
The submitter states that, when the distillation is essentially complete, there is a tendency for the residue to foam; this should be watched for and the heat should be turned back to avoid carryover into the distillate. The checkers did not experience any difficulties of this sort.
10.
The checkers found that the commercial grade of "dried"
magnesium sulfate was not completely effective and, even after three treatments with fresh drying agent, the subsequent distillation afforded an azeotrope of
neopentyl alcohol and water of b.p.
80–85°. The organic layer of the azeotrope had to be separated from the water, dried, and redistilled to give the stated total yields.
11.
The fraction between 95° and 110° should be taken off at a high reflux ratio; toward the end of the distillation the reflux ratio should again be increased. Most of the product comes over at 113°.
12.
Pure
neopentyl alcohol melts at about
55°. From time to time it will be necessary to circulate hot water through the take-off condenser in order to facilitate removal of the alcohol.
3. Discussion
Neopentyl alcohol has been made by
lithium aluminum hydride reduction of
trimethylacetic acid2 and by treating
tert-butylmagnesium chloride with
methyl formate.
3
The preparation of neopentyl alcohol from diisobutylene herein described represents an example of acid-catalyzed addition of hydrogen peroxide to a branched olefin, followed by an acid-catalyzed rearrangement of the tertiary hydroperoxide formed. In addition to neopentyl alcohol, there are formed acetone and also small amounts of methanol and methyl neopentyl ketone by an alternative rearrangement of the hydroperoxide.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
diisobutylene
sulfuric acid (7664-93-9)
methanol (67-56-1)
ether (60-29-7)
sodium bicarbonate (144-55-8)
acetone (67-64-1)
hydrogen peroxide (7722-84-1)
methyl formate (107-31-3)
Trimethylacetic acid (75-98-9)
magnesium sulfate (7487-88-9)
lithium aluminum hydride (16853-85-3)
hydroperoxide
2,2-Dimethyl-1-propanol,
Neopentyl alcohol (75-84-3)
hydrogen peroxide-sulfuric acid
methyl neopentyl ketone (590-50-1)
tert-butylmagnesium chloride (677-22-5)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved