9H-fluorene-2-carboxaldehyde.

The title compound, C14H10O, crystallized in the centrosymmetric space group P2(1)/c with a single molecule in the asymmetric unit. The C-H...O interaction having the shortest C...O distance involves the ring-bridging C9 atom and one of its H atoms, and results in the formation of a cyclic dimer about a center of symmetry. The molecular core is nearly planar. The dihedral angle between the best-fit plane of the ring to which the aldehyde group is attached and the plane of the aldehyde group is 4.4 (9) degrees. In a number of respects the molecular disposition is similar to that previously determined for the geometrically similar dibenzofuran-4-carboxaldehyde molecule.