Organic Syntheses, CV 3, 576
Submitted by Ralph Mozingo and L. A. Patterson.
Checked by Nathan L. Drake and Homer Carhart.
1. Procedure
A solution of
258 g. (3 moles) of washed and dried methyl acrylate in
500 ml. of anhydrous ether is placed in a
1-l. round-bottomed flask. The flask is fitted with a
rubber stopper carrying a
drying tube and an
8-mm. glass inlet tube for
hydrogen bromide. The inlet tube, which extends almost to the bottom of the flask, is connected through a
1-l. safety trap to a
hydrogen bromide generator (Note
2). The flask with its contents is placed in an
ice bath, and
245 g. (3.03 moles) of anhydrous hydrogen bromide is passed into the solution (Note
3). After the
hydrogen bromide has been added, the flask is stoppered and allowed to stand for about 20 hours at room temperature.
The
ether is removed by distillation (Note
4) from a
hot-water bath. At the end of the distillation, the water bath is heated to 80–85°, and when no more liquid comes over at this temperature the residue is transferred to a
500-ml. modified Claisen distilling flask and distilled under reduced pressure. The
methyl β-bromopropionate distils at
64–66°/18 mm. and weighs
410–428 g. (
80–84%) (Note
5) and (Note
6).
2. Notes
1.
Methyl acrylate in methanol is available from Rohm and Haas Company, Philadelphia, Pennsylvania. Since the ester polymerizes in the presence of peroxides, it is necessary to add some
hydroquinone as an inhibitor. The ester should not be stored for long periods of time, even when it contains
hydroquinone. Storage should be in a refrigerator.
3. The addition may be as rapid as is convenient without the loss of ether due to the exothermic reaction.
4. The ether may be removed under anhydrous conditions and used for a subsequent preparation of the ester without further treatment.
5.
Ethyl β-bromopropionate may be prepared in the same manner in about
90% yield. The boiling point of the ethyl ester is
77–79°/19 mm.
6. The residue consists largely of
β-bromopropionic acid which may be recovered by distillation, b.p.
115–120°/18 mm., followed by recrystallization from
carbon tetrachloride. The yield of this acid has never been more than
5% of the theoretical amount.
3. Discussion
This preparation is referenced from:
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