N-Cyclohexyl-3-fluorobenzamide

In the title molecule, C13H16FNO, the amide (N—C=O) plane is oriented at an angle of 29.9 (2)° with respect to the aromatic ring. The cyclohexane ring adopts the usual chair conformation. In the crystal structure, intermolecular N—H⋯O hydrogen bonds link the molecules into chains along [100]. A weak C—H⋯F interaction is also observed. The F atom is disordered over two positions with occupancy factors of 0.873 (3) and 0.127 (3).

In the title molecule, C 13 H 16 FNO, the amide (N-C O) plane is oriented at an angle of 29.9 (2) with respect to the aromatic ring. The cyclohexane ring adopts the usual chair conformation. In the crystal structure, intermolecular N-HÁ Á ÁO hydrogen bonds link the molecules into chains along [100]. A weak C-HÁ Á ÁF interaction is also observed. The F atom is disordered over two positions with occupancy factors of 0.873 (3) and 0.127 (3).   Table 1 Hydrogen-bond geometry (Å , ).

Comment
The background to this study has been described in an earlier paper (Saeed et al., 2008b).
The molecular structure of the title compound is related to that of the 2,4-dichloro compound (Saeed et al., 2008a). The cyclohexane ring is in the most stable chair conformation. In general, bond lengths and angles are within normal ranges. The aromatic ring C2-C7 is oriented with respect to the N1/O1/C1 plane at a dihedral angle of 29.9 (2)°. The N1-C1-C2-C7 torsion angle is 150.37 (15)°, for the reported dichloro compound the corresponding angle is 130.16 (18)°.
In the crystal structure, intermolecular N-H···O hydrogen bonds (Table 1) link the molecules into infinite chains along the [100] direction ( Fig. 2), in which they may be effective in the stabilization of the structure. Another intermolecular interaction is C-H···F (Table 1), as found in 4-fluoro-N-(2-fluorophenyl)benzamide (Chopra & Row, 2005).
Experimental 3,5-Difluorobenzoyl chloride (5.4 mmol) in CHCl 3 was treated with cyclohexylamine (21.6 mmol) under a nitrogen atmosphere at reflux for 4 h. Upon cooling, the reaction mixture was diluted with CHCl 3 and washed consecutively with aq 1 M HCl and saturated aq NaHCO 3 . The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure. Crystallization of the residue in CHCl 3 afforded the title compound (84%). Analysis calculated for C 13 H 15 F 2 NO: C 65.26, H 6.32, N 5.85%; found: C 65.31, H 6.39, N 5.77%.

Refinement
The F atom is disordered over two positions (F1 and F2) with site occupation factors of 0.873 (3) for F1 and 0.127 (3) for F2. H atoms were initially located in difference syntheses, but were then included in the refinement, at calculated positions, in the riding-model approximation, with N-H = 0.88 Å and C-H = 0.95-1.00 Å. The isotropic displacement parameters were set equal to 1.2Ueq of the carrier atom. In the absence of significant anomalous scattering effects, the Friedel pairs were merged.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.