(+/-)-3-Oxocyclopentanecarboxylic acid: The smallest keto acid known to aggregate by catemeric hydrogen bonding.

The title compound, C6H8O3, is the smallest keto acid yet found to aggregate in the solid as acid-to-ketone hydrogen-bonded catemers. Four translational chains pass through the cell in the a direction [O...O = 2.6915 (14) A and O-H...O = 166 degrees]. Two intermolecular C-H...O close contacts exist, involving both carbonyl functions.