Fluoren-9-one oxime

In the title molecule, 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 intramolecular C—H⋯O generates an S(6) ring. In the crystal, molecules related by a twofold screw axis are connected by O—H⋯N hydrogen bonds, forming [100] chains Within these chains, molecules related by a unit translation along [100] show π–π stacking interactions between their fluorene ring systems with an interplanar distance of 3.347 (2) Å. The dihedral angle between the fluorene units of adjacent molecules along the helix is 88.40 (2)°. There is a short C—H⋯π contact between the fluorene groups belonging to neighbouring chains.

In the title molecule, C 13 H 9 NO, 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 intramolecular C-HÁ Á ÁO generates an S(6) ring. In the crystal, molecules related by a twofold screw axis are connected by O-HÁ Á ÁN hydrogen bonds, forming [100] chains Within these chains, molecules related by a unit translation along [100] showstacking interactions between their fluorene ring systems with an interplanar distance of 3.347 (2) Å . The dihedral angle between the fluorene units of adjacent molecules along the helix is 88.40 (2) . There is a short C-HÁ Á Á contact between the fluorene groups belonging to neighbouring chains.

Related literature
For the original procedure for the preparation of the title compound, see: Moore & Huntress (1927). For the use of the title compound as a starting material for the synthesis of bioactive compounds, see: Amlaiky et al. (1983); Ni et al.  Hydrogen-bond geometry (Å , ).
Supporting information for this paper is available from the IUCr electronic archives (Reference: GK2601).

Comment
The title compound, which was prepared according to a known procedure (Moore & Huntress, 1927) has found extensive use as a starting material for preparation of medicinal active compounds such as novel cyclophilin A inhibitors (Ni et al., 2009), novel analogs of beta-adrenoceptor antagonists (Rad et al., 2012) and beta-blocker (Amlaiky et al., 1983).
The ring atoms, N and O atoms in the title compound molecule, are essentially coplanar with a maximum deviation of 0.079 (2) Å for the O atom from the averaged ring plane (13 carbon atoms). The molecule in the crystal exhibits a C12-H12···O1 intramolecular interaction (Table 1), (Figure 1). The molecules related by a twofold screw axis are connected by O1-H1···N1 hydrogen bonds (Table 1)

Refinement
All carbon-bound hydrogen atoms, except the H of the OH group which was freely refined, were placed in calculated positions with C-H distance of 0.95 Å and refined as riding with Uiso(H) = 1.2Ueq(C).

Figure 1
A view of the title molecule with displacement ellipsoids shown at the 50% probability level, showing the intramolecular contact within the molecule.