In a
1-l. round-bottomed flask equipped with an efficient water condenser are placed
148 g. (2 moles) of ethyl formate (b.p.
52–53°) and
150 ml. of 95% ethanol. One hundred and twenty grams
(2 moles) of 85% hydrazine hydrate is added cautiously to this solution (Note
1) with shaking over a period of 10 minutes. After the reaction has subsided, the solution is refluxed on a
steam bath for 18 hours. The bulk of the water and
ethanol is now removed by evaporation under reduced pressure until the volume in the flask is about 150 ml. The resulting syrup, crude
formhydrazide, is heated under atmospheric pressure for 3 hours, during which time the temperature of the bath is raised from 150° to 200°. After cooling to about 100°, the oil is taken up in
50 ml. of 95% ethanol, and
5 g. of Norite is added. The filtered solution is then diluted with
75 ml. of ether and placed in an
icebox to cool. The crystalline product is filtered, washed with
50 ml. of 1:2 ethanol-ether, and dried. The yield of
aminotriazole, melting at
77–78°, is
55–60 g. (
65–71%) (Note
2). If a purer product is desired, the crude, washed material may be recrystallized, using
2 ml. of warm 95% ethanol per gram of compound followed by the addition of
2.5 ml. of ether, and chilling. The melting point of the purified product is
81–82°.
The residual amine in the filtrate may be isolated in the form of the hydrochloride. The combined solutions are evaporated on a steam bath,
50 ml. of concentrated hydrochloric acid is added, and heating is continued for 2 hours. On cooling, the syrupy solution crystallizes. It is triturated with
50 ml. of ethanol, and the
4-amino-1,2,4-triazole hydrochloride is filtered, washed with a little
ethanol, and dried. The yield of the hydrochloride is
10–18 g. (
8–15%); the salt melts at
147–148° and may be recrystallized from
95% ethanol, using 10 ml. per gram; the melting point is thus raised to
151–152°.