rac-5-(1-Methylethyl)-2-sulfanylideneimidazolidin-4-one

In the title compound, C6H10N2OS, the 2-sulfanylideneimidazolidin-4-one fragment is essentially planar (r.m.s. deviation = 0.0033 Å). In the crystal, one amino group is involved in N—H⋯O hydrogen bonding, which links pairs of molecules into inversion dimers, while the other amino group generates weak N—H⋯S hydrogen bonds, which link these dimers into chains in [10-1]. The chains are further aggregated into layers parallel to the ac plane through weak C—H⋯O interactions.

In the title compound, C 6 H 10 N 2 OS, the 2-sulfanylideneimidazolidin-4-one fragment is essentially planar (r.m.s. deviation = 0.0033 Å ). In the crystal, one amino group is involved in N-HÁ Á ÁO hydrogen bonding, which links pairs of molecules into inversion dimers, while the other amino group generates weak N-HÁ Á ÁS hydrogen bonds, which link these dimers into chains in [101]. The chains are further aggregated into layers parallel to the ac plane through weak C-HÁ Á ÁO interactions.
Intermolecular N-H···O hydrogen bonds (Table 1) lead to centrosymmetric dimers formation. Weak interactions of type N-H···S (Table 1) mediate the formation of the chains along [101], which are further linked into layers parallel to ac plane through the weak C-H···O interactions (Table 1).

Experimental
The procedure employed for synthesis of compound (I) was described by Wang et al. (2006). A mixture of D-valine (2.34 g, 0.2 mol) and thiourea (4.57 g, 0.6 mol) was added in a flask and heated under stirring. The reaction was remained in the oil bath at temperature of 190°C for 30 minutes, after this period, the flask was allowed to cool down and water (20 ml) was added while the flask was still warm. The solution was reheated to dissolve all the solids and allowed to cool to room temperature, then placed in a refrigerator for 3 h. The solid were removed by vacuum filtration and storage.
Recrystallization from chloroform yielded single crystals suitable for X-ray analysis.

Refinement
All H atoms were placed in calculated positions (N-H = 0.86 Å; C-H = 0.96-0.98 Å) and treated as riding atoms, with U iso (H) = 1.2-1.5 U eq of the parent atom.

rac-5-(1-Methylethyl)-2-sulfanylideneimidazolidin-4-one
Crystal data Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.50440 (