rac-N-[Hydroxy(4-pyridyl)methyl]picolinamide: a hemiamidal

The title compound, C12H11N3O2, a hemiamidal, was synthesized by solvent-free aldol condensation at room temperature by grinding picolinamide with isonicotinaldehyde in a 1:1 molar ratio. In the molecule, the two pyridine rings are inclined to one another by 58.75 (6)°. They are linked, at positions 2 and 4, by the hemiamidal bridge (–CO—NH—CHOH–). The NH-group H atom forms an intramolecular hydrogen bond with the N atom of the picolinamide pyridine ring. In the crystal, symmetry-related molecules are linked via N—H⋯O hydrogen bonds, involving the NH group H atom of the hemiamidal bridge and the hydroxy O atom, forming inversion-related dimers, with graph-set R 2 2(8). Adjacent molecules are also linked via O—H⋯N hydrogen bonds, involving the hydroxy substituent and the 4-pyridine N atom. Together these interactions lead to the formation of double-stranded ribbon-like hydrogen-bonded polymers propagating in [010]. The latter are further connected via C—H⋯O hydrogen bonds involving the carbonyl O atom, so forming a two-dimensional network in (011).

The title compound, C 12 H 11 N 3 O 2 , a hemiamidal, was synthesized by solvent-free aldol condensation at room temperature by grinding picolinamide with isonicotinaldehyde in a 1:1 molar ratio. In the molecule, the two pyridine rings are inclined to one another by 58.75 (6) . They are linked, at positions 2 and 4, by the hemiamidal bridge (-CO-NH-CHOH-). The NH-group H atom forms an intramolecular hydrogen bond with the N atom of the picolinamide pyridine ring. In the crystal, symmetry-related molecules are linked via N-HÁ Á ÁO hydrogen bonds, involving the NH group H atom of the hemiamidal bridge and the hydroxy O atom, forming inversion-related dimers, with graph-set R 2 2 (8). Adjacent molecules are also linked via O-HÁ Á ÁN hydrogen bonds, involving the hydroxy substituent and the 4-pyridine N atom. Together these interactions lead to the formation of doublestranded ribbon-like hydrogen-bonded polymers propagating in [010]. The latter are further connected via C-HÁ Á ÁO hydrogen bonds involving the carbonyl O atom, so forming a two-dimensional network in (011).

Experimental
Data collection: X-AREA (Stoe & Cie, 2004); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 and PLATON. Green chemistry is a well established field of research, enhanced by its numerous applications in high technology industries and because of the need for environmentally friendly syntheses. The perfect green reaction has been described as one which: proceeds at room temperature, requires no organic solvent, is highly selective and exhibits high atom efficiency, yet produces no waste products (Raston & Scott, 2000). In recent decades, numerous reactions using mechanical activation have been reported to give 100% yield (Kaupp, 2005). This procedure has a number of advantages, such as rapid and qualitatively solvent free synthesis and no necessary work up procedure (Kaupp, 2003). On the other hand, there are some disadvantages, such as the use of harmful sodium hydroxide, or other sodium salts, as intermediates in the reaction work up. The title compound was synthesized by grinding picolinamide with isonicotinaldehyde in a molar ratio of 1:1 giving a brown gelatinous material. On drying in air a brown microcrystalline powder was obtained, which proved to be the title compound. The compound is a result of the combination of green chemistry and mechanical activation.
The latter is the only non-cyclic example of such a (-CO-NH-CHOH-) unit that was found during a search of the Cambridge Crystal Structure Database (CSD, V5.31, last update May 2010; Allen et al., 2002).
In the title molecule the two pyridine rings are inclined to one another by 58.75 (6) °, and the NH H-atom (H2N) forms an intramolecular hydrogen bond with the picolinamide N-atom (N1) ( Fig. 1 and Table 1).
In the crystal molecules are linked via N-H···O and O-H···O hydrogen bonds (Table 1). The N-H···O hydrogen bonds, involving the hemiamidal NH group and the hydroxyl O-atom, lead to the formation of inversion dimers, graph-set R 2 2 (8) (Fig. 2) (Bernstein et al., 1995). Adjacent molecules are linked via O-H···N hydrogen bonds involving the hydroxyl H-atom (H2O) and the adjacent pyridine N-atom, N2 (Table 1). Together with molecules related by an inversion center these interactions lead to a graph-set of R 4 4 (14) (Fig. 3). Finally these hydrogen bonding interactions lead to the formation of double-stranded ribbon-like polymers propagating in [010]. They are further linked via C-H···O interactions, involving the C═O O-atom, leading to the formation of two dimensional networks stacking along [100] (Fig. 4 and Table 1).

Refinement
The NH and OH H-atoms were located in a difference electron-density map and were freely refined: O-H = 0.905 (19) Å, N-H = 0.875 (17) Å. The C-bound H-atoms were included in calculated positions and treated as riding atoms: C-H = 0.95 Å for H-aromatic, and 1.00 Å for H-methine, with U iso (H) = 1.2U eq (C).     Table 1 for details).

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 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 Rfactors(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.  (17)