Sodium ethoxide is prepared from
46 g. (2 gram atoms) (Note 1) of sodium and
800 ml. of absolute ethanol in a
2-l. three-necked flask equipped with
stirrer and a
reflux condenser. To the hot solution is added
113 g. (106 ml., 1 mole) of ethyl cyanoacetate followed by
108 g. (98 ml., 1 mole) of phenylhydrazine (Note
2), and the mixture is stirred and heated in an
oil bath at 120° for 16 hours. Then most of the
ethanol is removed under reduced pressure and the residue is dissolved in 1 l. of water; the mixture is warmed to about 50° and stirred to facilitate solution. After being cooled to room temperature, the solution is extracted with three
100-ml. portions of ether (Note
3). The aqueous phase is acidified by the addition of
100 ml. of glacial acetic acid, cooled in ice, and filtered. The crude product is washed on the filter with
100 ml. of 95% ethanol; it is then transferred to a flask and boiled with 500 ml. of the same solvent, and this mixture is cooled and filtered. The solid is washed with
ethanol and dried. The tan crystalline
1-phenyl-3-amino-5-pyrazolone, melting with decomposition at
216–218°, weighs
76–82 g. (
43–47%) (Note
4).