Phenanthrene-9-carboxylic Acid

The title compound, C₁₅H₁₀O₂, crystallized in the centrosymmetric space group C2/c. Hydrogen bonding is of the cyclic dimer type about a center of symmetry. The carboxyl H and O atoms are ordered. The phenanthrene core is almost planar and the dihedral angle between the core plane and the carboxyl group plane is only 1.8 (1)°. The bay H atoms, H4 and H5, lie close to the core plane and 2.02 (2) Å from each other; the refinement places them on opposite sides of the core plane, but this result has little statistical significance.

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