1-(3-nitrophenyl)-3-carboxy-5-pyrazolone

1-(3-nitrophenyl)-5-oxo-4H-pyrazole-3-carboxylic acid

5-keto-1-(3-nitrophenyl)-4H-pyrazole-3-carboxylic acid

1-(3-Nitrophenyl)-5-oxo-2-pyrazoline-3-carboxylic acid

4,5-dihydro-1-(3-nitrophenyl)-5-oxo-1H-pyrazole-3-carboxylic acid