(±)-2,3-Dihydro-3-oxo-1H-indenecarboxylic Acid: Hydrogen-Bonding Patterns in a γ-Keto Acid and its Monohydrate

Crystal structures have been determined for the title compound in both its anhydrous, (I), C₁₀H₈O₃, and monohydrate, (II), C₁₀H₈O₃.H₂O, forms. In (I), helical monoenantiomeric hydrogen-bonding (carboxyl-to-ketone) catemers, counteraligned with chains of the opposite chirality, pass through the cell in the b direction; a close contact of 2.57 Å is found between the sp² carboxyl O atom and aromatic H6 atom on a neighboring mol­ecule of the same chirality. The hydrate (II) displays a complex hydrogen-bonding pattern in which each water mol­ecule participates in three hydrogen bonds to three different keto acid mol­ecules. A 2.54 Å close contact is found between the ketone and aromatic H4 atom on a neighboring centrosymmetrically related mol­ecule, as well as a 2.54 Å close contact between H1 and the ketone of a mol­ecule of identical chirality translated one cell in the a direction.

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