Org. Synth. 1958, 38, 16
DOI: 10.15227/orgsyn.038.0016
DIBROMOACETONITRILE
[Acetonitrile, dibromo-]
Submitted by James W. Wilt and James L. Diebold
1.
Checked by B. C. Mckusick and H. E. Knipmeyer.
1. Procedure
A solution of 63.8 g. (0.75 mole) of cyanoacetic acid (Note 1) in 750 ml. of cold water is placed in a 2-l. beaker. N-Bromosuccinimide (267 g., 1.5 moles) (Note 2) is added in portions with good mechanical stirring over a period of about 6 minutes (Note 3). The slightly exothermic reaction which attends the separation of the dibromoacetonitrile as a heavy oil is completed in about 20 minutes, after which time the beaker is placed in an ice bath and allowed to cool for 2 hours (Note 4).
The precipitated succinimide is collected on a large Büchner funnel atop a 2-l. filter flask and is washed with six 50-ml. portions of methylene chloride. The lower organic layer in the filtrate is separated from the aqueous phase, which is extracted with two 25-ml. portions of methylene chloride. The organic layer and the extracts are combined, washed vigorously with 50 ml. of a 5% sodium hydroxide solution (Note 5) and three 80-ml. portions of water, and dried over 10 g. of anhydrous sodium sulfate for several hours in a flask wrapped with aluminum foil (Note 6).
The colorless dried oil is distilled through a 45-cm. Widmer column (Note 7). Most of the methylene chloride is removed by heating the contents of the distillation pot to 75° at atmospheric pressure. The pressure is then lowered to about 20 mm., and 112–129 g. (75–87%) of dibromoacetonitrile is collected as a colorless oil, b.p. 70–72°/20 mm., nD25 1.540–1.542, d420 2.369 (Note 8) and (Note 9).
2. Notes
1.
Commercial cyanoacetic acid (Eastman Kodak Company), m.p. 67–71.5°, about 98% pure, was found satisfactory for this preparation.
2.
N-Bromosuccinimide obtained from Matheson, Coleman and Bell, Inc., as well as from Arapahoe Chemicals, Inc., was used as received. The
N-chlorosuccinimide (Note 9) was commercial material from Arapahoe Chemicals, Inc.3.
The
N-bromosuccinimide should be added as rapidly as possible consistent with the foaming produced by evolution of
carbon dioxide.
4.
About one-third of the
succinimide (50–53 g.) precipitates from the solution during the cooling period, thus rendering the subsequent purification of the nitrile easier. Sometimes the solution must be seeded to start the precipitation. The checkers found it necessary to store the mixture in a refrigerator over-night in order to obtain
50–53 g. of succinimide.
5.
The basic aqueous phase becomes pink through action of the base on
dibromoacetonitrile.
6.
Pure
dibromoacetonitrile is fairly stable to air and light, but traces of basic impurities cause it to become discolored
(Note 5). Protective shielding retards this coloration.
7.
Unless an efficient column is used, some nitrile distils over with the
methylene chloride. The checkers used a
120-cm. spinning-band column.
8.
The product shows good shelf stability, but, as a precautionary measure, it is best stored under
nitrogen in a
sealed brown vessel.
Dichloroacetonitrile (Note 9) is less sensitive and may be stored in an ordinary
glass-stoppered brown bottle.
9.
In exactly the same fashion, from
63.8 g. (0.75 mole) of cyanoacetic acid and
200.3 g. (1.5 moles) of N-chlorosuccinimide there may be obtained
45–54 g. (
55–65%) of colorless
dichloroacetonitrile, b.p.
110–112°/760 mm.,
nD25 1.439,
d420 1.369. Since this reaction is slightly slower, 30 minutes should be allowed for the reaction before chilling.
3. Discussion
Dibromoacetonitrile has been prepared by the dehydration of
dibromoacetamide with
phosphorous pentoxide2,3 and by the present method.
4 An early report that
dibromoacetonitrile can be obtained from
cyanoacetic acid by treatment with
bromine,
5 a method similar to that described here, was later shown to be wrong.
2 Dibromoacetonitrile has been prepared also by the bromination of
ethyl cyanoacetate in the presence of
magnesium oxide.
6
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
phosphorous pentoxide
sodium hydroxide (1310-73-2)
bromine (7726-95-6)
sodium sulfate (7757-82-6)
nitrogen (7727-37-9)
carbon dioxide (124-38-9)
Ethyl cyanoacetate (105-56-6)
cyanoacetic acid (372-09-8)
Dibromoacetonitrile,
Acetonitrile, dibromo- (3252-43-5)
N-chlorosuccinimide (128-09-6)
dibromoacetamide
methylene chloride (75-09-2)
Succinimide (123-56-8)
magnesium oxide (1309-48-4)
N-bromosuccinimide (128-08-5)
dichloroacetonitrile (3018-12-0)
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