Crystal structure of 4-oxo-4H-chromene-3-carb­oxy­lic acid

In the title compound, C(10)H(6)O(4), also known as 3-carb­oxy­chromone, the non-H atoms of the chromone ring are essentially coplanar (r.m.s. deviation = 0.0057 Å), with the maximum deviation from their least-squares plane [0.011 (2) Å] being for a pyran C atom. The dihedral angle between the fused ring and plane of the carb­oxy group is 3.06 (2)°. An intra­molecular hydrogen bond is formed between the ring carbonyl O atom and the carb­oxy O—H atom, closing an S(6) loop. In the crystal, mol­ecules are assembled by stacking inter­actions [centroid–centroid distance between the benzene and pyran rings = 3.844 (3) Å] and C—H⋯O hydrogen bonds, generating a three-dimensional network. Short contacts are also observed between the carb­oxy O and C atoms [C=O⋯C=O = 3.002 (3) Å].