Crystal structure of N-[(naphthalen-1-yl)carbamothioyl]cyclohexanecarboxamide

The title compound, C18H20N2OS, displays whole-molecule disorder over two adjacent sets of sites with an occupancy ratio of 0.630 (11):0.370 (11). In each disorder component, the cyclohexyl ring shows a chair conformation with the exocyclic C—C bond in an equatorial orientation. The dihedral angles between the cyclohexyl ring (all atoms) and the naphthyl ring system are 36.9 (6) for the major component and 20.7 (12)° for the minor component. Each component features an intramolecular N—H⋯O hydrogen bond, which closes an S(5) ring. In the crystal, inversion dimers linked by pairs of N—H⋯S hydrogen bonds generate R 2 2(8) loops for both components. Aromatic π–π stacking interactions [shortest centroid–centroid separation = 3.593 (9) Å] and a C—H⋯π interaction are also observed.


S1. Comment
The design and synthesis of thiourea are of considerable interest because of their use in agriculture, medicine and analytical chemistry (J·H. Hu et al., 2011). Thiourea derivatives are driven by their potential as biological active compounds (Sun et al., 2006) and in the material application such as anti corrosion (Shen et al., 2006). As part of our own studies in this area, the crystal structure of the title compound has been determined and the results are presented herein. angles between cyclohexane and benzene rings (C5-C8/C10) and (C5-C10) of naphthalene moiety are 37.0 (7)and 36.5 (7)° (major component). In the case of minor component, the dihedral angles between cyclohexane and benzene rings (C5-C8/C10)and (C5-C10) of naphthalene are 37.0 (7)and 36.5 (7)°, respectively. The molecular conformation is consolidated by an intramolecular N-H···O hydrogen bond, forming S(5) ring motif.

S2. Experimental
A solution of cyclohexane carbonyl chloride (1.4661 g, 10 mmol) in acetone (60 ml) was added drop wise to a suspension of potassium thiocyanate (0.9718 g, 10 mmol) in anhydrous acetone (60 ml). The reaction mixture was heated under reflux for 45 minutes and then cooled to room temperature. A solution of substituted naphthalen-1-amine (1.43 g, 10 mmol) in acetone (60 ml) was added and the resulting mixture was stirred for 2 h at room temperature. Hydrochloric acid (0.1 N, 500 ml) was added and the resulting white solid was filtered off, washed with water and dried in vaccum. The yield of the isolated product was 89%, giving colourless blocks.

S3. Refinement
All H atoms were fixed geometrically and allowed to ride on their parent C atoms, with C-H distances fixed in the range 0.93-0.97 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for all other H atoms.  The molecular structure of the major component of the title compound, with displacement ellipsoids drawn at 40% probability level.

Figure 2
Stick plot of both major and minor components of the title compound, with the atoms label for non-H atoms.

Figure 3
The crystal packing of the title compound, viewed along the b axis. The hydrogen bonds are shown as dashed lines (see Table 1 for details).