4,4′-Bipyridine acetic acid disolvate

The crystal structure of the title compound, C10H8N2·2C2H4O2, is built up from 4,4′-bipyridine and acetic acid molecules linked by strong O—H⋯N hydrogen bonds. The 4,4′-bipyridine and the two acetic acid molecules are further connected through weak C—H⋯O hydrogen bonds to form a supramolecular two-dimensional network parallel to the (001) plane. The two pyridine rings make a dihedral angle of 31.8 (1)°.

The crystal structure of the title compound, C 10 H 8 N 2 Á2C 2 H 4 O 2 , is built up from 4,4 0 -bipyridine and acetic acid molecules linked by strong O-HÁ Á ÁN hydrogen bonds. The 4,4 0 -bipyridine and the two acetic acid molecules are further connected through weak C-HÁ Á ÁO hydrogen bonds to form a supramolecular two-dimensional network parallel to the (001) plane. The two pyridine rings make a dihedral angle of 31.8 (1) .
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: DN2279).
The asymmetric unit of (I) contains one 4,4-bipyridine molecule and two acetic acid molecules linked trough strong O-H···O hydogen bonds (Fig. 1). The two pyridine rings are both planar, with a RMS deviation of fitted atoms being 0.0033 Å and 0.0074 Å, respectively. The dihedral angle between them is 31.8 (1) °.

Experimental
A mixture of 2,2-bipyridine (5 mmol, 0.78 g) and acetic acid (10 mmol, 0.60 g) in water (10 ml) was stirred for 2 h, and filtrate was allowed to evaporate at room temperature. Colorless single crystals of the title compound were formed after two weeks.

Refinement
All H atoms attached to C atoms and O atom were fixed geometrically and treated as riding with C-H = 0.93 Å (aromatic) or 0.96 Å (methyl) and O-H = 0.82 Å with U iso (H) = 1.2U eq (C aromatic or O) or U iso (H) = 1.5U eq (Cmethyl).
In the absence of significant anomalous scattering, the absolute structure could not be reliably determined and then the Friedel pairs were merged and any references to the Flack parameter were removed.    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.