Org. Synth. 1940, 20, 64
DOI: 10.15227/orgsyn.020.0064
METHYL β-BROMOPROPIONATE
[Propionic acid, β-bromo-, methyl ester]
Submitted by Ralph Mozingo and L. A. Patterson.
Checked by Nathan L. Drake and Homer Carhart.
1. Procedure
Six hundred and fifty grams of a 60% solution of methyl acrylate in methanol to which has been added 4 g. of hydroquinone (Note 1) is washed, successively, with 800-ml., 400-ml., and 200-ml. portions of a 7% sodium sulfate solution. The methyl acrylate layer is dried by shaking with 45 g. of anhydrous sodium sulfate for 20–30 minutes. The ester is then removed from the sodium sulfate by filtration and used without distillation. The yield is 280–325 g.
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
Methyl β-bromopropionate has been prepared by the esterification of
β-bromopropionic acid with
methyl alcohol alone
1 and through the use of
hydrogen bromide as a catalyst,
2 and by the direct addition of
hydrogen bromide to
methyl acrylate.
2
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
methyl alcohol,
methanol (67-56-1)
ether (60-29-7)
hydroquinone (123-31-9)
phenol (108-95-2)
hydrogen bromide (10035-10-6)
bromine (7726-95-6)
sodium sulfate (7757-82-6)
carbon tetrachloride (56-23-5)
β-Bromopropionic acid (590-92-1)
Ethyl β-bromopropionate (539-74-2)
methyl acrylate (96-33-3)
METHYL β-BROMOPROPIONATE,
Propionic acid, β-bromo-, methyl ester (3395-91-3)
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