Org. Synth. 1943, 23, 35
[Acetic acid, benzoyl-, ethyl ester]
Submitted by S. M. McElvain and K. H. Weber.
Checked by R. L. Shriner and C. H. Tilford.
A 2-l. three-necked flask is mounted on a steam bath and fitted with a reflux condenser, a separatory funnel, and an efficient sealed stirrer. In the flask is placed 600 ml. of absolute ethanol, and to this is added gradually 46 g. (2 gram atoms) of clean sodium cut into small pieces. The sodium ethoxide solution is stirred and cooled to room temperature, after which 267 g. (260 ml., 2.05 moles) of ethyl acetoacetate (Note 1) is added slowly through the separatory funnel. The reflux condenser is then replaced by a short still head, and the ethanol is removed by distillation at approximately room temperature and under the pressure of a water pump. When approximately half the ethanol has been removed, sufficient sodium enolate precipitates so that stirring has to be discontinued. When the residue appears dry (after about 2 hours) the last traces of ethanol are removed by heating for an hour on the steam bath under a pressure of 2 mm. The flask is allowed to cool to room temperature under reduced pressure.
To the cooled residue of sodium enolate is added 600 g. (570 ml., 4 moles) of ethyl benzoate. The steam bath is replaced by an oil bath, and the temperature of the bath is raised to 140–150° and maintained there for 6 hours. Then, over a period of another hour, the temperature of the bath is gradually raised to 180° (Note 2). The distillate that is collected during this period of heating amounts to 200–210 g. and consists chiefly of ethyl acetate and ethanol.
The reaction mixture is cooled, 250 ml. of water is added, and the mixture is made acid to litmus by addition of a cooled solution of 100 g. of concentrated sulfuric acid in 200 ml. of water. Chipped ice is added if necessary to keep the mixture cool. The upper ester layer is separated, and the aqueous layer is extracted with 200 ml. of ether. The combined ether and ester layers are shaken with 350 ml. of a saturated sodium bicarbonate solution until no more carbon dioxide is evolved, and then the organic layer is washed with 200 ml. of water. The water layer is combined with the sodium bicarbonate solution and extracted with 400 ml. of ether. The combined ether and ester layers are dried over sodium sulfate. The ether is removed by distillation on the steam bath, and the excess ethyl benzoate and acetoacetic ester (Note 3) are then removed by distillation under reduced pressure through a 15-cm. fractionating column. Finally, the ethyl benzoylactetate is distilled (Note 3) at 101–106° /1 mm. (130–135° /3 mm.). The yield of ester boiling over a 5° range is 190–210 g. (50–55% based on the ethyl acetoacetate).
Commercial ethyl acetoacetate
was distilled, and the fraction boiling at 68–69° /11 mm. was used.
During the last hour of heating about 20 g. of the ethyl acetate
A mixture of ethyl acetoacetate
and ethyl benzoate
(100–150 g.) was collected at 75–90° /12 mm., after which 250–300 g. of pure ethyl benzoate
, b.p. 90–93° /12 mm., was recovered. These products were removed through a 15-cm. fractionating column. The remaining ethyl benzoylacetate
was distilled through a short still head without a fractionating column.
Methods of preparation are listed in an earlier volume.1
In addition ethyl benzoylacetate
has been prepared by the reaction of benzoyl chloride
with the magnesium enolate of malonic ester2
and subsequent decomposition with β-naphthalenesulfonic acid
and by the condensation of acetophenone
with ethyl carbonate
in the presence of sodium hydride
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
sulfuric acid (7664-93-9)
ethyl acetate (141-78-6)
sodium bicarbonate (144-55-8)
sodium sulfate (7757-82-6)
carbon dioxide (124-38-9)
β-naphthalenesulfonic acid (120-18-3)
benzoyl chloride (98-88-4)
sodium ethoxide (141-52-6)
ethyl benzoate (93-89-0)
Ethyl acetoacetate (141-97-9)
Acetic acid, benzoyl-, ethyl ester (94-02-0)
sodium hydride (7646-69-7)
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