Org. Synth. 1950, 30, 43
[Acetic acid, cyanophenyl-, ethyl ester]
Submitted by E. C. Horning and A. F. Finelli1
Checked by William S. Johnson and H. Wynberg.
Sodium ethoxide is prepared from 12.0 g. (0.52 g. atom) of sodium and 300 ml. of anhydrous ethanol in a 1-l. three-necked round-bottomed flask fitted with a reflux condenser carrying a calcium chloride tube. After the sodium has dissolved completely, the condenser is arranged for distillation under reduced pressure and the excess ethanol is removed by heating the flask on a steam bath while the system is maintained at the pressure obtained with an ordinary aspirator (Note 1).
As rapidly as possible, after removal of the ethanol, the flask is fitted with a rubber-sealed stirrer, a dropping funnel, a distilling head containing a thermometer, and a condenser arranged for distillation into a flask protected by a calcium chloride tube. There are then added 300 ml. (292 g., 2.5 moles) of dry diethyl carbonate, 80 ml. of dry toluene, and 58.5 g. (0.50 mole) of phenylacetonitrile (Note 2). The flask is heated, with good stirring, and the cake of sodium ethoxide soon dissolves. When distillation has started, dry toluene is added dropwise at about the same rate that the distillate is collected. Approximately 200–250 ml. of toluene should be added in a period of 2 hours (Note 3) while stirring and distillation are continued.
The mixture is cooled and transferred to a 1-l. beaker. After addition of 300 ml. of cold water, the aqueous phase is acidified with 35–40 ml. of acetic acid. The layers are separated and the water solution is extracted with three 75-ml. portions of ether. The organic solutions are combined, washed with 100 ml. of water, and dried over anhydrous magnesium sulfate. The low-boiling solvents are removed by distillation at atmospheric pressure, and the residue is distilled under reduced pressure through a short (15-cm.) Vigreux column. After a 1–5 g. forerun, the product is collected at 125–135°/3–5 mm. (Note 4). The yield is 66–74 g. (70–78%).
The success of this procedure is dependent upon the quality of the sodium ethoxide
. The ethanol
should be dried before use,2
and the sodium ethoxide
should not be heated to a temperature higher than 90–100°. The dry material can be transferred, but in this case it is advisable to prepare it in the flask in which it is to be used.
should be distilled before use. The diethyl carbonate
are dried by distillation.
remaining in the sodium ethoxide
, together with the ethanol
produced during the reaction, is removed during this period. The progress of the carbethoxylation reaction can be followed by temperature readings. During the first half of the heating period distillation usually occurs at a vapor temperature of 80–85°, but as the reaction nears completion and the ethanol
is removed, the temperature rises to 110–115°. Near the end of the period, the sodium salt of ethyl phenylcyanoacetate
appears as a precipitate.
Other observed boiling points are 129–131°/3 mm.
, 145–150°/7–8 mm.
The product is a colorless liquid, nD25
This procedure is a modification of the method of Wallingford, Jones, and Homeyer.3
The carbethoxylation of phenylacetonitrile
is the only method of preparative value for this compound.
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
sodium salt of ethyl phenylcyanoacetate
acetic acid (64-19-7)
sodium ethoxide (141-52-6)
magnesium sulfate (7487-88-9)
diethyl carbonate (105-58-8)
Acetic acid, cyanophenyl-, ethyl ester (4553-07-5)
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