Fluoren-9-one oxime.

In the title mol-ecule, C13H9NO, the fluorene system and the oxime group non-H atoms are essentially coplanar, with a maximum deviation from the fluorene mean plane of 0.079 (2) Å for the oxime O atom. A short intra-molecular C-H⋯O generates an S(6) ring. In the crystal, mol-ecules related by a twofold screw axis are connected by O-H⋯N hydrogen bonds, forming [100] chains Within these chains, mol-ecules related by a unit translation along [100] show π-π stacking inter-actions between their fluorene ring systems with an inter-planar distance of 3.347 (2) Å. The dihedral angle between the fluorene units of adjacent mol-ecules along the helix is 88.40 (2)°. There is a short C-H⋯π contact between the fluorene groups belonging to neighbouring chains.