3-Oxocyclo­butane­carboxylic acid: hydrogen bonding in a small-ring γ-keto acid

The title ketocarboxylic acid, C(5)H(6)O(3), is the smallest carboxy­cyclanone to have its crystal structure determined. It adopts a chiral conformation, by rotation of its carboxyl O atoms away from the plane of skeletal symmetry that passes through the carboxyl carbon and both atoms of the ketone carbonyl. The four-membered ring is non-planar, with a shallow fold of 14.3 (1)° along a line connecting the two α-carbons of the ketone group. In the crystal, the molecules are linked by centrosymmetric hydrogen-bond pairing of ordered carboxylic acid groups [O⋯O = 2.6392 (12) Å and O—H⋯O = 175.74 (15)°], yielding two different sets of dimers, related by by a 2(1) screw axis in c, in the cell. A C—H⋯O interaction is also present.