A solution of
sodium ethoxide is prepared from
23 g. (1 g. atom) of sodium and
250 ml. of anhydrous ethanol in a
1-l. round-bottomed flask fitted with a
reflux condenser carrying a
calcium chloride drying tube. After the
sodium has dissolved, the solution is cooled and
113 g. (1 mole) of ethyl cyanoacetate is added (Note
1). This mixture is allowed to stand while a second solution of
sodium ethoxide of the same volume and concentration is prepared. To this solution is added
97 g. (1.02 moles) of guanidine hydrochloride. The
sodium chloride is separated by filtration, and the clear filtrate containing
guanidine is added to the solution of
ethyl sodiocyanoacetate. This mixture is heated for 2 hours under reflux and is then evaporated to dryness at atmospheric pressure. The solid product is dissolved in 325 ml. of boiling water and acidified with
67 ml. of glacial acetic acid. Upon cooling of the solution,
101–103 g. (
80–82%) of yellow needles separates; m.p.
260–270° (dec.) (Note
2).