2-Amino-4,6-dimethylpyrimidine–sorbic acid (1/1)

In the crystal of the title compound, C6H9N3·C6H8O2, the 2-amino-4,6-dimethylpyrimidine and sorbic acid molecules are linked through N—H⋯O and O—H⋯N hydrogen bonds, which generate a cyclic bimolecular heterosynthon with an R 2 2(8) graph-set motif. Further, two inversion-related pyrimidine molecules are base-paired via a pair of N—H⋯N hydrogen bonds, forming a cyclic bimolecular homosynthon with a graph-set of R 2 2(8). A discrete hetero tetrameric supramolecular unit along the b axis is formed by the fusion of two heterosynthons and one homosynthon. An aromatic π–π interaction [centroid–centroid distance = 3.7945 (16) Å] is observed between these tetrameric units.

In the crystal of the title compound, C 6 H 9 N 3 ÁC 6 H 8 O 2 , the 2amino-4,6-dimethylpyrimidine and sorbic acid molecules are linked through N-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds, which generate a cyclic bimolecular heterosynthon with an R 2 2 (8) graph-set motif. Further, two inversion-related pyrimidine molecules are base-paired via a pair of N-HÁ Á ÁN hydrogen bonds, forming a cyclic bimolecular homosynthon with a graph-set of R 2 2 (8). A discrete hetero tetrameric supramolecular unit along the b axis is formed by the fusion of two heterosynthons and one homosynthon. An aromaticinteraction [centroid-centroid distance = 3.7945 (16) Å ] is observed between these tetrameric units.

Sundaramoorthy Gomathi and Packianathan Thomas Muthiah Comment
The non-covalent interactions of aminopyrimidine with carboxylic acid derivatives are of immense significance, since they involve in many molecular recognition process of biological functions and protein-drug binding (Hunt et al.,1980). The primary supramolecular synthon is assembled via N-H···O and O-H···N hydrogen bonds between the carboxylic group of SA and the amino pyrimidine moiety of AMPY to form a cyclic bimolecular heterosynthon with an R 2 2 (8) graphset motif (Etter, 1990;Bernstein et al., 1995). Two centrosymmetric AMPY molecules are self-assembled to form complementary base pairing via a pair of N-H···N hydrogen bonds to form another R 2 2 (8) ring motif. The complementary base pairing involves 2-amino group and ring N3 i atom of inversion related pyrimidine moiety of AMPY.
The primary and secondary interactions lead to the generation of a discrete and stable linear hetero tetramer along the b axis (Ebenezer & Muthiah, 2012) which is a four-component supramolecule formed by the fusion of two centrosymmetric bimolecular heterosynthons [R 2 2 (8)] and a homosynthon [R 2 2 (8)] (Fig. 2). These discrete linear hetero tetrameric units are arranged in two dimensional space as sheets without any neighbouring interactions in the same plane.
The pyrimidine moiety of inversion related linear heterotetrameric units present in the parallel planes are stacked by an aromatic π-π interaction in a head to tail fashion ( Fig. 3) with the interplanar distance of 3.580 Å, centroid to centroid distance of 3.7945 (16) Å [Cg-Cg i ; symmetry code: (i) 1 -x,1 -y,1 -z] and the slip angle of 19.36°.

Experimental
Hot aqueous solutions of 2-amino-4, 6-dimethylpyrimidine (31 mg, Aldrich) and sorbic acid (28 mg, Sisco) were mixed in a 1:1 molar ratio. The resulting solution was warmed over a water bath for half an hour and then kept at room temperature for crystallization. After a week, colorless prismatic crystals were obtained.

Refinement
The hydrogen atoms for NH 2 and OH groups were located in a difference Fourier map and refined freely. All other hydrogen atoms were positioned geometrically (C-H = 0.93-0.96 Å) and were refined using a riding model, with U iso (H) = 1.2U eq (C) for CH or 1.5U eq (C) for CH 3 .

Figure 1
The asymmetric unit of the title compound, shown in 30% probability displacement ellipsoids.   Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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 N1 0.2301 (