Organic Syntheses, CV 3, 615
Submitted by George Bosworth Brown
Checked by Lee Irvin Smith and Vincent J. Webers.
1. Procedure
The procedure should be carried out under a
hood since the poisonous
hydrogen cyanide may be evolved.
In a
3-l. flask provided with a
reflux condenser are placed
114 g. (1.0 mole) of ethyl crotonate (Note
1),
460 ml. of 95% ethanol, and a solution of
54 g. (1.06 moles) of 95% sodium cyanide in 128 ml. of water. The solution is refluxed on a
steam bath for 5 hours, during which time some
ammonia is evolved and the solution becomes dark yellow. A suspension of
150 g. of barium hydroxide octahydrate in 286 ml. of hot water is added to the solution, and the mixture is concentrated under reduced pressure (about 30 mm.) to a volume of about 400 ml. It is again refluxed on the steam bath for 4 hours or until the evolution of
ammonia almost ceases (Note
2). The solution is then concentrated to a thick paste under reduced pressure.
The residue is cooled and dissolved in
171 ml. of nitric acid (sp. gr. 1.4) (Note
3), and the solution is warmed for 30 minutes on the steam bath. It is immediately concentrated to complete dryness under reduced pressure (Note
4). The flask is cooled,
300 ml. of benzene is added, and the mixture is refluxed for a short time to render the cake friable. The
benzene is removed by decantation, and the cake is pulverized and extracted six times by refluxing it briefly with
300-ml. portions of ether. The combined
benzene and ether extracts are filtered and concentrated to a volume of about 225 ml. In the mean-time the residual salts are extracted twice by refluxing them vigorously for a short time with
300-ml. portions of benzene. The
benzene solutions are separated by decantation and added to the
ether concentrate. The distillation is then continued until about two-thirds of the
benzene has been removed, when the
benzene solution is poured into a
beaker and allowed to cool. The
methylsuccinic acid is collected on a filter and is washed by shaking a suspension of it in
150 ml. of chloroform (Note
5). The yield of air-dried product, melting at
110–111°, amounts to
87–93 g. (
66–70%) (Note
6).
2. Notes
2. The checkers refluxed the mixture for 8 hours at this point; traces of
ammonia were still present. Most of the
ammonia was evolved in 4 hours, however.
5. If a series of runs is to be made, the
chloroform may be used repeatedly.
6. The submitter states that the same percentage yield is obtained when four times the above quantities of reagents are used.
3. Discussion
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