Methods for production of 1,2,4-triazol-3-one
Novel methods for producing 1,2,4-triazol-3-one from semicarbazide hydrochloride and formic acid are provided. In methods of this invention, ethanol is used in removal of unreacted formic acid to increase yield and purity of produced 1,2,4-triazol-3-one.
1. A method for producing 1,2,4-triazol-3-one comprising (i) combining semicarbazide hydrochloride and formic acid to form an initial composition, (ii) heating the initial composition to a temperature of at least 70° C. and maintaining the temperature for at least 1 hour to form a product composition, (iii) distilling the product composition to remove a portion of unreacted formic acid and form a concentrated product slurry, (iv) slurrying the concentrated product slurry in ethanol to form an ethanol slurry, and heating the ethanol slurry to at least 40° C. over a period of at least 10 minutes, (v) collecting crude 1,2,4-triazol-3-one from the ethanol slurry, (vi) combining the crude 1,2,4-triazol-3-one with water and heating to dissolve crude 1,2,4-triazol-3-one to form a product solution, (vii) cooling the product solution to lower than 10° C., and (viii) collecting recrystallized 1,2,4-triazol-3-one from the product solution.
2. The method of claim 1 wherein the formic acid is combined in up to 7 equivalents as to the semicarbazide hydrochloride.
3. The method of claim 1 wherein the cooling is conducted over a period of at least 2.5 hours.
4. The method of claim 1 further comprising (ix) drying the recrystallized 1,2,4-triazol-3-one under vacuum.
5. A method for producing 1,2,4-triazol-3-one comprising (i) combining semicarbazide hydrochloride and formic acid to form an initial composition in amounts such that the formic acid is combined in up to 7 equivalents as to the semicarbazide hydrochloride, (ii) heating the initial composition to a temperature of at least 70° C. and maintaining the temperature for at least 1 hour to form a product composition, (iii) distilling the product composition to remove at least a portion of unreacted formic acid and form a concentrated product slurry, (iv) slurrying the concentrated product slurry in ethanol to form an ethanol slurry, and heating the ethanol slurry to at least 40° C. over a period of at least 10 minutes, (v) collecting crude 1,2,4-triazol-3-one from the ethanol slurry, (vi) combining the crude 1,2,4-triazol-3-one with water, and heating to at least 70° C. to form a product solution, (vii) cooling the product solution to lower than 10° C. over a period of at least 2.5 hours, (viii) collecting recrystallized 1,2,4-triazol-3-one from the product solution, and (ix) drying the recrystallized 1,2,4-triazol-3-one.