Organic Syntheses, CV 3, 302
Submitted by Lee Irvin Smith, W. W. Prichard, and Leo J. Spillane.
Checked by Nathan L. Drake and Harry D. Anspon.
1. Procedure
A 5-l. round-bottomed three-necked flask is equipped with a Kyrides sealed stirrer and two long condensers, and the apparatus is so arranged that, if necessary, the exit water from the condensers may be quickly used to cool the flask.
In the flask are placed
200 ml. of dioxane,
100 g. (1.02 moles) of mesityl oxide, and a solution of
4.6 moles of potassium hypochlorite in 3 l. of water (Note
1), and the stirrer is started. The mixture becomes warm immediately, and within 5 minutes
chloroform begins to reflux. When the reaction becomes very vigorous the stirrer is stopped and the flask is cooled with running water (Note
2). The stirring is resumed as soon as feasible and is continued for 3–4 hours, when the temperature of the mixture will have dropped to that of the room.
Sodium bisulfite (about 5 g.) is then added to react with the excess
hypochlorite (Note
3).
One of the condensers is then replaced by a
dropping funnel, and enough
50% sulfuric acid (about 200 ml.) is added, with stirring and cooling, to make the solution acid to
Congo red paper. When the solution has cooled, it is extracted with eight
400-ml. portions of ether (Note
4). The
ether extract is
carefully distilled on a
steam bath until the
ether and
chloroform are removed.
The residue is then placed in a
modified Claisen flask and distilled under reduced pressure.
Dimethylacrylic acid distils at
100–106°/20 mm. The yield of white solid is
49–53 g. (
49–53%). This product melts at
60–65°. It may be further purified by recrystallization from
petroleum ether (b.p.,
60–70°) or water (Note
5).
2. Notes
2. The flask is cooled only as much as is necessary to keep the
chloroform refluxing gently. After 30 minutes the reaction will have subsided enough so that no further cooling is necessary.
4. It is important that the ether be
well shaken with the solution during the extractions.
5. For recrystallization from water, 48–50 g. of the acid is dissolved in 450 ml. of hot water. The solution is cooled in ice for several hours, and the crystalline precipitate is filtered with suction and dried overnight in a
desiccator. The yield of pure
dimethylacrylic acid melting at
66–67.5° is
35–40 g., a recovery of
70–83%.
3. Discussion
This acid has been prepared from various α-haloisovaleric acid derivatives by elimination of the halogen together with one of the β-hydrogen atoms;
1,2,3,4 from
β-hydroxyisovaleric acid derivatives by elimination of water;
5,6,7 by action of
sodium isobutoxide on
iodoform;
8 by the condensation of
malonic acid with
acetone;
9,10,11 by the reaction of
acetone and
ketene;
12 by condensation of acetoacetic ester with
acetone and action of
barium hydroxide on the product,
isopropylidene acetoacetic ester;
13 by the action of alkali upon
2,4-dibromo-2-methyl-butanone;
14 by the incomplete ozonolysis of
phorone;
15 by the action of alcoholic
potassium hydroxide upon
2,5,5,7-tetramethylocta-2,6-diene-4-one;
16 by the action of
potassium hydroxide on
isopropenylacetic acid;
17 by the action of
aluminum chloride on
α,α-dimethylsuccinic anhydride;
18 by metallating
isobutylene with
amylsodium, carbonating, and acidifying;
19 by the action of hypohalites on
mesityl oxide;
20,21,22 and by the action of
sulfuric acid on
3-methyl-3-butenoic acid.
23
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