Pyrimidine-2-carboxamide

In the crystal strucuture of the title compound, C5H5N3O, which was obtained upon recrystallization of 2-cyanopyrimidine from aqueous sodium hydroxide, the amide group is twisted with respect to the aromatic ring by 24.9 (1)°. π–π stacking is observed between partially overlapped rings at a face-to-face separation of 3.439 (6) Å. The structure features a centrosymmetric pair of intermolecular N—H⋯O hydrogen bonds. Another N—H⋯O hydrogen bond between adjacent molecules links them into a helical chain motif.

In the crystal strucuture of the title compound, C 5 H 5 N 3 O, which was obtained upon recrystallization of 2-cyanopyrimidine from aqueous sodium hydroxide, the amide group is twisted with respect to the aromatic ring by 24.9 (1) .stacking is observed between partially overlapped rings at a face-to-face separation of 3.439 (6) Å . The structure features a centrosymmetric pair of intermolecular N-HÁ Á ÁO hydrogen bonds. Another N-HÁ Á ÁO hydrogen bond between adjacent molecules links them into a helical chain motif.

Comment
In order to study the nature of π-π stacking, a series of metal complexes incorporating substituted benzoate ligand have been prepared in our laboratory (Cheng et al., 2000;Xu & Xu, 2004). As a continuing work, metal complexes with pyrimidine-2-carboxylate ligand have recently been prepared (Zhang et al., 2007). In the process of preparing pyrimidine-2-carboxylic acid from cyanopyrimidine, the title compound has been obtained.
The molecular structure of the title complex is shown in Fig. 1. The bond distances and angles are normal. The amide group is twisted with respect to the benzene ring by a dihedral angel of 24.92 (12)°. The amino group links with carbonyl groups of adjacent molecules via O-H···O hydrogen bonding (Table 1). π-π stacking is observed between parallel, partially overlapped N1-pyrimidine and N i -pyrimidine rings ( Fig. 1) [symmetry code: (i) 1 − x, 1 − y, 1 − z], face-to-face separation being 3.439 (6) Å; similar to the situation found in the pyrimidine-2-carboxylate complex of copper(II) (Zhang et al., 2007).
Experimental 2-Cyanopyrimidine (1.0 g, 9.5 mmol) was dissolved in 10 ml water, then a NaOH solution (0.1 M) was dropped to the solution until to pH = 12. Single crystals of the title compound were obtained from the solution after one week.

Refinement
Amino H atoms were located in a difference Fourier map and refined as riding in as-found relative positions with U iso (H) = 1.5U eq (N). Other H atoms were placed in calculated positions with C-H = 0.93 Å and refined in riding mode with U iso (H) = 1.2U eq (C). Fig. 1 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 > 2sigma(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.