In a
3-l. round-bottomed flask equipped with a reflux condenser are placed
582 g. (2.5 moles) of N-tricarboxylic ester (p. 415) and
800 g. (6.7 moles) of 42% hydrazine hydrate (Note
1). The flask is shaken by hand to mix the two layers. After a short time, reaction begins with considerable evolution of heat, and all the
N-tricarboxylic ester goes into solution (Note
2). After the reaction subsides, the solution is heated for 1 hour on a
steam bath and then evaporated under reduced pressure until the mixture becomes a thick slurry of
diaminobiuret crystals (Note
3). The mixture is cooled,
2 l. of 95% ethanol is added, and the
diaminobiuret which has crystallized is filtered, washed with
250 ml. of ethanol, and dried. The substance melts at
205° with decomposition. The yield is
115–125 g. (
69–75%).
The filtrate is now evaporated at atmospheric pressure to remove the
ethanol, and the residual oil is distilled using a
Vigreux column.
Ethyl hydrazinecarboxylate boils at
92–95° /13 mm. The yield is
350–370 g. (
90–95%). After distillation in vacuum, the ester may crystallize; the crystals melt at
51–52°.