Crystal structures of pyridine and pyridine trihydrate

Abstract

The crystal structure of pyridine is orthorhombic with space group Pna21, a = 1752.4(3), b = 896.9(2), and c = 1135.2(2) pm at 153 K and Z = 16. A low melting crystalline hydrate of pyridine was found by DTA to be a trihydrate. It is orthorhombic, too, with space group Pbca, a = 1244.4(3), b = 1783.2(6), and c = 679.1(2) pm at 223 K and Z = 8. Both structures were determined from single crystal MoKα diffractometer data and refined to unweighted R values of 0.044 for 2769 and of 0.074 for 932 observed independent reflections. Most apparent in the anhydrous structure is an arrangement of the molecular noncrystallogrpahic twofold axes in layers perpendicular to the c-axis direction and separated by c/4. With the ring centers not far from the points of a bcc lattice a ’’molecular coordination number’’ of 14 can be assigned to each of the four independent molecules. Their geometries are very similar and close to mm-C2v symmetry. In the structure of the trihydrate the water molecules are O–H ⋅ ⋅ ⋅ O hydrogen bonded in a new pattern of condensed four, five, and six-membered rings to form buckled layers, separated by b/2, which enclose the pyridine molecules. There is one hydrogen bond O–H ⋅ ⋅ ⋅ N from a water molecule to the pyridine molecule. All hydrogen atoms are ordered.

Association in Dilute Aqueous Solution of Pyridine and Its Methyl Derivatives Studied by Cryoscopic Method

“…In the liquid system, remnants of the crystalline structures are in dynamic equilibrium with the less structured "fluid" phase. Unfortunately, only two relevant crystal structures are known: those of pyridine and 4-methylpyridine trihydrates [7,8,18]. In these structures, hydrogen-bonded water molecules form two-dimensional layers with protons protruding on either side, through which the amine molecules are connected.…”

“…Contrary to 2,6-dimethylpyrine, pyridine and 4-methylpyridine form solid trihydrates rather than monohydrates [7,8]. However, the pyridine trihydrate melts incongruently forming ice and a liquid aqueous solution of pyridine [9].…”

Viscosity of Associated Mixtures Approximated by the Grunberg-Nissan Model

“…As the molecular order in liquids may resemble that in the solid phase, some information can be gained from the crystallographic data. Although the structures of solid hydrates of 2-methylpyridine and 2,6-dimethylpyridine have not been described yet [21,22], the structures of pyridine and 4-methylpyridine trihydrates [23][24][25] may give an idea about the aggregation. In the trihydrates, hydrogen-bonded water molecules form twodimensional layers with protons protruding on either side, through which the amine molecules are connected (Fig.…”

An X-ray crystallographic study of 1,2,5- and 1,3,5-triazapentadienium salts, C6H14N3+.ClO4−, C6H14N3+.ClO4−, C6H14N3+.C6H2N3O7−

“…The observed trends in the bond angles within the delocalized systems of compounds (2)-(3) may be explained in terms of non-bonded interactions and lone-pair repulsions. Thus the narrow angle at the central nitrogen atom of (2a) [115.9 (7)°], which is similar to that of pyridine (116.6 °) (Mootz & Wussow, 1981), is presumably due to lone-pair effects. The angle at N(2) of structures (3a) and (3b), weighted mean 120.6 (6) ° , is rather wider, and this may be caused by competing effects of lone-pair repulsions, and of non-bonded interactions between the 1-(Z)-methyl group [C(ll)] and the central hydrogen atom, H(3).…”

“…The effect of the replacement of CH groups in delocalized systems by nitrogen atoms has most often been studied with cyclic model compounds. The comparison of pyridine with benzene is a classic example (Mootz & Wussow, 1981). From a structural point of view, the incorporation of two relatively short C--N bonds into the cyclic structure causes significant distortion, especially of the bond angles, but the role of the nitrogen atom itself remains unclear.…”