Redetermination of 2-methyl-4-nitro-pyridine N-oxide.

An improved crystal structure of the title compound, C6H6N2O3, is reported. The structure, previously solved [Li et al. (1987 ▶). Jiegou Huaxue (Chin. J. Struct. Chem.), 6, 20-24] in the ortho-rhom-bic space group Pca21 and refined to R = 0.067, has been solved in the ortho-rhom-bic space group Pbcm with data of enhanced quality, giving an improved structure (R = 0.0485). The mol-ecule adopts a planar conformation with all atoms lying on a mirror plane. The crystal structure is composed of mol-ecular sheets extending parallel to the ab plane and connected via C-H⋯O contacts involving ring H atoms and O atoms of the N-oxide and nitro groups, while van der Waals forces consolidate the stacking of the layers.

2,2'-Dimethyl-4,4'-bipyridine.

In the crystal structure of the title compound, C(12)H(12)N(2), the mol-ecule is twisted around the central C-C bond, with a dihedral angle of 8.32 (5)° between the mean planes of the pyridyl rings. The crystal structure is stabilized by arene stacking inter-actions, with a distance of 3.81 (1) Šbetween the ring centroids.