4-Hydroxyantipyrine

The molecular structure of the title compound, 1,2-dihydro-4-hydroxy-1,5-dimethyl-2-phenyl-3H-pyrazol-3-one, C₁₁H₁₂N₂O₂, has been determined. Both rings are planar and make a dihedral angle of 42.5 (1)° with one another. In the crystal structure, the molecule is stabilized as a centrosymmetric hydrogen-bonded dimer. There is no conjugation between the phenyl and pyrazole rings.

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