4-Chloro-6-methoxypyrimidin-2-amine–succinic acid (2/1)

The asymmetric unit of the title compound, 2C5H6ClN3O·C4H6O4, consists of one 4-chloro-6-methoxypyrimidin-2-amine molecule and one half-molecule of succinic acid which lies about an inversion centre. In the crystal, the acid and base molecules are linked through N—H⋯O and O—H⋯N hydrogen bonds, forming a tape along [1-10] in which R 2 2(8) and R 4 2(8) hydrogen-bond motifs are observed. The tapes are further interlinked through a pair of C—H⋯O hydrogen bonds into a sheet parallel to (11-2).

The asymmetric unit of the title compound, 2C 5 H 6 ClN 3 OÁ-C 4 H 6 O 4 , consists of one 4-chloro-6-methoxypyrimidin-2amine molecule and one half-molecule of succinic acid which lies about an inversion centre. In the crystal, the acid and base molecules are linked through N-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds, forming a tape along [110] in which R 2 2 (8) and R 4 2 (8) hydrogen-bond motifs are observed. The tapes are further interlinked through a pair of C-HÁ Á ÁO hydrogen bonds into a sheet parallel to (112).

sup-1
Acta Cryst.  (Condon et al., 1993). For example, imazosulfuron, ethirmol and mepanipyrim have been commercialized as agrochemicals (Maeno et al., 1990). Pyrimidine derivatives have also been developed as antiviral agents, such as AZT, which is the most widely-used anti-AIDS drug (Gilchrist, 1997). The dicarboxylic acid, succinic acid, is a precursor for many chemicals of industrial importance (Zeikus et al., 1999;Song & Lee, 2006). In order to study some interesting hydrogen bonding interactions, the synthesis and structure of the title compound, (I), is presented here.
The asymmetric unit of the title compound consists of a 4-chloro-6-methoxypyrimidin-2-amine molecule and a half of the succinic acid molecule (Fig. 1). The acid molecule is lying about an inversion centre. The 4-chloro-6-methoxypyrimidin-2-amine molecule is approximately planar, with a maximum deviation of 0.037 (1) Å for atom O1. The bond lengths (Allen et al., 1987) and angle are normal.
In the crystal packing, the 4-chloro-6-methoxypyrimidin-2-amine molecules interact with the carboxylic group of the respective succinic acid molecules through N3-H2N3···O3 i and O2-H1O2···N2 i hydrogen bonds (symmetry code in Table 1), forming a hydrogen-bonded ring motif R 2 2 (8) (Bernstein et al., 1995). These motifs are centrosymmetrically paired via N3-H2N3···O3 hydrogen bonds, forming a complementary DADA array. These arrays are further interlinked with a neighboring array through a couple of C3-H3A···O1 ii hydrogen bonds (symmetry code in Table 1) combine together to form a large ring motif, with graph-set notation R 6 6 (34). These ring motifs extend to give a sheet parallel to (112) plane as shown in Fig. 2.

Experimental
Hot methanol solutions (20 ml) of 4-chloro-6-methoxypyrimidin-2-amine (36 mg, Aldrich) and succinic acid (29 mg, Merck) were mixed and warmed over a heating magnetic stirrer hotplate for a few minutes. The resulting solution was allowed to cool slowly at room temperature and crystals of the title compound (I) appeared after a few days. H= 0.95-0.99 Å) and were refined using a riding model, with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C). A rotating group model was used for the methyl group. Three outliers were omitted (-4 5 3, -1 2 1 and 1 0 1) in the final refinement.

Figure 1
The molecular structure of the title compound with atom labels with 50% probability displacement ellipsoids.  The crystal packing of the title compound. The H atoms not involved in the intermolecular interactions (dashed lines) have been omitted for clarity.  (Cosier & Glazer, 1986) operating at 100.0 (1) K. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > σ(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.