2-Hy­droxy-7-nitro­cyclo­hepta-2,4,6-trien-1-one

The title compound, also known as 7-nitro­tropolone, C₇H₅NO₄, exists in the crystalline state as the 2-hy­droxy-7-nitro­cyclo­hepta-2,4,6-trien-1-one tautomer and not as 2-hy­droxy-3-nitro­cyclo­hepta-2,4,6-trien-1-one. The dihedral angle between the ring and the nitro group is 70.3 (2)°. In the crystal, neighbouring mol­ecules are linked into dimers by a pair of O—H...O hydrogen bonds. In addition, the crystal is stabilized by O...π [3.4039 (14) Å] and O...O [3.073 (2) Å] inter­actions.