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A quantity comprising 69.0 gm (0.547 mol) of 1-methyl-1H-pyrazole-5-carboxylic acid of m.p.: 227°-228° C. (R. Huttel and M. E. Schon, Liebigs Ann. Chem 625, 55 [1959]) was added in small portions to a mixture of 200 ml of concentrated sulfuric acid and 60 ml of 90% fuming nitric acid under stirring. The temperature of the mixture rose from 75° C. at the beginning to a maximum temperature of 95° C. After the exothermal reaction was finished, heating was continued for 30 minutes up to 95° C. The cold mixture was stirred into 300 gm of cracked ice, and the resulting ice-cold suspension was filtered off by suction filtration. The filtration residue was washed with water, and after recrystallization from ethyl acetate, 44.0 gm (47% of theory) of pale yellow crystals were obtained.

1. customrose from 75° C. at the beginning to a maximum temperature of 95° C
2. customAfter the exothermal reaction
3. temperatureheating
4. filtrationthe resulting ice-cold suspension was filtered off by suction filtration
5. washThe filtration residue was washed with water
6. customafter recrystallization from ethyl acetate, 44.0 gm (47% of theory) of pale yellow crystals
7. customwere obtained