Formic Acid → 3H-1,2,4-Triazol-3-one

Participants

Reaction Conditions

Reaction Steps

Aqueous semicarbazide free base feedstock (523.8 grams) was prepared from 64 percent N2H4 (4.18 moles) and urea (4.17 moles) by the method of Example 1. Thirty-seven percent hydrochloric acid (205.6 grams, 2.08 moles) and 90 percent formic acid (533.3 grams, 10.44 moles) were successively added to the aqueous semicarbazide free base. The mixture was heated to 107°-110° C. for four hours; a formic acid-H2O azeotrope distilled (610.5 grams), followed by H2O addition (160 ml) and resumption of stripping (107 grams). After cooling to 10° C., the mother liquor was siphoned (307 grams). The crude 1,2,4-triazol-5-one was recrystallized from H2O (760 ml). After cooling to 10° C., the supernatant liquid was siphoned (807 grams) and the product was slurried with an additional 210 ml H2O (10° C.), filtered, and vacuum-dried to give 168.5 grams of 1,2,4-triazol-5-one (1.98 moles, 47.4 percent yield based on N2H4 charged), m.p. 236.5°-8° C. (Cl-, 0.22 percent).

Provenance & Evidence