4-Methylpyridine (C6H7N) has been studied at 120 K by combined x-ray and neutron diffraction. It crystallizes in the space group I41a: a=7.618(5) Å, c=18.635(10) Å, and Z=8. The crystal structure was solved by direct methods and refined to RF =0.059 (x-ray data) and RF =0.035 (neutron data), respectively, after reducing the intensities of the meroedrically twinned crystals. The resulting X–N synthesis agrees well with the theoretically calculated (4-31G+BF) dynamic electron deformation density.
Das quasibinäre System H2O‐HF enthält drei intermediäre Phasen der Zusammensetzungen 1:1, 1:2 und 1:4, die bei −36, −78 (Zersetzung) und −100°C schmelzen. Mit 1:2‐Zusammensetzung gibt es auch noch eine Tieftemperaturphase (Umwandlung bei −103°C) und eine metastabile Phase. Die 1:1‐Phase kristallisiert orthorhombisch, Raumgruppe Pnma, z = 4, a = 621,6, b = 418,4, c = 623,3 pm bei −62°C. Eine der 1:2‐Phasen (die Zuordnung steht noch aus) kristallisiert monoklin, Raumgruppe P21/c, z = 4, a = 347,8, b = 603,9, c = 1141,5 pm, β = 96,57° bei −95°C. Beide Kristallstrukturen sind die von Oxoniumsalzen, H3OF bzw. H3OFHF, und durch starke Wasserstoffbrücken geprägt.
2-Pyridone, C 5 H 5 NO, has been studied by single crystal diffraction at 295 Κ and 120 Κ using X-ray and neutron diffraction methods. The crystal structure of this compound was first studied by Penfold [Acta Crystallogr. 6, 591 -600 (1953)] but described in an unusual setting. We confirmed this structure at both temperatures and refined the structure in the usual setting. Deformation density studies based on the 120 Κ data were performed using the multipole and charge cloud models. They are compared with the theoretical (4 -31G + BF) dynamic deformation density.
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