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. Ninety-eight percent sulfuric acid (99.8 grams, 0.998 mole) and 90 percent formic acid (510.6 grams, 9.99 moles) were successively added to the aqueous semicarbazide free base. After reflux at 108°-110° C. for four hours, a formic acid/H2O azeotrope was stripped, H2O (160 ml) was added to the concentrate and stripping resumed at 118°-125° C. to give 595 grams of combined distillate. The reaction mixture was cooled to 10° C. and the mother liquor was siphoned (58 grams). Crude 1,2,4-triazol-5-one was recrystallized from H2O (725 ml), the supernatant liquid was siphoned (930 grams), and 200 ml H2O was added for product filtration. Vacuum-drying gave 152.6 grams of 1,2,4-triazol-5-one (1.80 moles, 43.1 percent yield based on N2H4 charged), m.p. 234°-236° C. (Cl-, 0.02 percent).

Provenance & Evidence