2-(Octadecylsulfanyl)-1,3-thiazole

The title compound crystallizes with a linear alkyl chain bound to the sulfur atom at the 2-position of the thiazole ring.

The title compound, C 21 H 39 NS 2 , crystallizes with two molecules in the asymmetric unit, both having a linear 18-carbon alkyl chain bound through a thioether group. Nostacking or hydrogen bonding is observed. The orientation of the alkyl chains facilitates intermolecular interactions between te chains. The structure is metrically orthorhombic but crystallizes in the monoclinic space group P2 1 and was found to be twinned by pseudomerohedry (emulating orthorhombic symmetry) and by inversion. The twin factions refined to 0.37 (4), 0.13 (4), 0.31 (5), and 0.19 (4).

Structure description
The title compound ( Fig. 1) exhibits no notable hydrogen bonding orinteractions. It appears that interactions involving atoms of the alkyl chains form the majority of the intermolecular interactions [DÁ Á ÁA = 3.730 (10) to 3.974 (11) Å ]. There are two independent molecular units found in the structure, indicated by the atom label suffixes A and B. While the majority of the two molecules exhibit similar geometrical features, such as a linear alkyl chain, the two molecules differ in the C3-S2-C4-C5 torsion angles [177.9 (7) in molecule A and 70.6 (8) in molecule B. From the packing diagram (Fig. 2), it appears that molecule B adopts this torsion angle to facilitate the alkyl-chain interactions while avoiding any repulsive interactions with the thiazole ring of the adjacent molecule A.

data reports Synthesis and crystallization
A 250 ml round-bottom flask, oven dried, was paired with a Teflon-coated magnetic stir bar. 2-Mercaptothiazole (1.004 g, 1 equiv.) and 1-bromooctadecane (2.861 g, 1 equiv.) were dissolved into 150 ml of acetonitrile in the 250 ml round bottom flask, which was attached to a water-jacketed reflux condenser and placed into an oil bath. The hot plate was set to 82 C with stirring on and ran for 48 h, after which it was left to cool to room temperature. The solvent was then removed under reduced pressure and a white crystalline solid formed in high yield (92%).
The solid product was dissolved in boiling acetonitrile and laboratory parafilm was used to cover the vial, with one hole prodded at the top. Colorless crystals of the product formed over 12 d.  8, 118.7, 77.4, 77.1, 76.8, 34.7, 32.0, 29.8, 29.7, 29.6, 29.5, 29.3, 29.2, 28.8, 22.8, 14.2 Refinement Crystal data, data collection and structure refinement details are summarized in Table 1. The structure is metrically orthorhombic but crystallizes in the monoclinic space group P2 1 . Initial attempts to solve the structure in various orthorhombic space groups failed. A closer inspection of diffraction images showed the peaks to be a bit asymmetric, but they were not obviously split. Unit-cell angles were indecisive. Reflection statistics (XPREP; Sheldrick, 2008) indicated a high R sym value for orthorhombic and for two of the three possible monoclinic settings (> 1/5). The third monoclinic option had a low R sym (0.05). After relaxation of the default thresholds for maximum intensity for systematically absent reflections, XPREP indicated a 2 1 screw axis, but was indecisive regarding the presence of glide planes because of twin overlaps. Solution attempts in P2 1 in this monoclinic setting were able to localize some of the alkyl chains. The addition of a twin transformation matrix (1 0 0 0 À1 0 0 0 À1) (Rotax within WinGX; Farrugia, 2012) and iterative refinements allowed for the assignment of the remaining atoms from difference density maps. The initial Flack parameter indicated the presence of inversion twinning, and in the final model the structure was refined as four

Figure 2
Packing diagram for the title compound depicting the alkyl chain interactions between molecules.

Figure 1
The title compound shown with 50% probability ellipsoids.

data-1
IUCrData ( where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.98 e Å −3 Δρ min = −0.75 e Å −3 Absolute structure: Twinning involves inversion, so Flack parameter cannot be determined Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. The structure is metrically orthorhombic but crystallizes in P21. It was found to be twinned by pseudomerohedry (emulating orthorhombic symmetry) and by inversion and was refined as a 4-component inversion twin. Twin factions refined to 0.37 (4), 0.13 (4), 0.31 (5) and 0.19 (4). The outer ends of the C18 alkyl chain is ill defined due to large thermal libration and/or ill defined disorder. The outermost C-C bond distance in the two molecules was restrained to be similar, and a rigid bond restraint (RIGU) was applied for the four outermost carbon atoms of each molecule. C-H bond distances were constrained to 0.95 Å for thiazole C-H moieties, 0.99 Å for methylene CH 2 and 0.98 Å for methyl CH 3 moieties. U iso (H) values were set to 1.5 times U eq (C) for methyl groups, and 1.2 times U eq (C) CH and CH 2 groups.