Acta Cryst. (2013). C69, 93-100 [ doi:10.1107/S010827011204930X ]
Abstract: In order to study the preferred hydrogen-bonding pattern of 6-amino-2-thiouracil, C4H5N3OS, (I), crystallization experiments yielded five different pseudopolymorphs of (I), namely the dimethylformamide disolvate, C4H5N3OS·2C3H7NO, (Ia), the dimethylacetamide monosolvate, C4H5N3OS·C4H9NO, (Ib), the dimethylacetamide sesquisolvate, C4H5N3OS·1.5C4H9NO, (Ic), and two different 1-methylpyrrolidin-2-one sesquisolvates, C4H5N3OS·1.5C5H9NO, (Id) and (Ie). All structures contain R21(6) N-HO hydrogen-bond motifs. In the latter four structures, additional R22(8) N-HO hydrogen-bond motifs are present stabilizing homodimers of (I). No type of hydrogen bond other than N-HO is observed. According to a search of the Cambridge Structural Database, most 2-thiouracil derivatives form homodimers stabilized by an R22(8) hydrogen-bonding pattern, with (i) only N-HO, (ii) only N-HS or (iii) alternating pairs of N-HO and N-HS hydrogen bonds.
Formula: C4H5N3OS·2C3H7NO, C4H5N3OS·C4H9NO, C4H5N3OS·1.5C4H9NO and C4H5N3OS·1.5C5H9NO
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