Single-crystal neutron diffraction of urea-phosphoric acid: evidence for H-atom migration in a short hydrogen bond between 150 K and 350 K
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C. C. Wilson
Abstract
The structure of urea-phosphoric acid has been refined using single-crystal neutron diffraction data collected at seven temperatures in the range 150 K to 350 K. The structure is orthorhombic, space group Pbca, Z=8, a=17.453(5)-17.679(8), b=7.454(3)-7.483(4), c=8.963(3)-8.992(4) Å, V=1166.0–1189.6 Å3. The molecules are linked by a short intermolecular O···H···O hydrogen bond, with O···O ≈ 2.4 Å and <O···H···O ≈ 170°. At 150 K, this bond is markedly asymmetric, with O···H = 1.168(4) Å and H···O = 1.252(4) Å. However, at 300 K and above, the H-atom is essentially centred between the two O-atoms. This systematic shift in position of the H-atom (up to ≈ 0.04 Å) is significant in relation to the esd´s of the measurements. H-atom migration along a hydrogen bond with temperature has been observed previously with other species, including quinolinic acid, and the hydrogen phthalate anions of lithium hydrogen phthalate monohydrate. There is no evidence to support the notion that the H-atom within the O···H···O hydrogen bond in urea-phosphoric acid is disordered, and the diffraction data are consistent with the previously reported hypothesis of a single-minimum potential energy surface for the short hydrogen bond.
© 2001 Oldenbourg Wissenschaftsverlag GmbH
Articles in the same Issue
- Single-crystal neutron diffraction of urea-phosphoric acid: evidence for H-atom migration in a short hydrogen bond between 150 K and 350 K
- Determination, prediction, and understanding of structures, using the energy landscapes of chemical systems - Part I
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- Structural phase transition of GdGa2 at high pressure
- Absorption spectra of calcium tartaric and cadmium oxalate crystals, grown in gel and doped by chromium, cobalt and nickel
- Elastic and thermoelastic properties of selected organic crystals: acenaphthene, trans-azobenzene, benzophenone, tolane, trans-stilbene, dibenzyl, diphenyl sulfone, 2,2´-biphenol, urea, melamine, hexogen, succinimide, pentaerythritol, urotropine, malonic acid, dimethyl malonic acid, maleic acid, hippuric acid, aluminium acetylacetonate, iron acetylacetonate, and tetraphenyl silicon
- Structure and ferroelasticity of tetramethylammonium-hexafluoroosmate(IV), (TMA)2[OsF6]
Articles in the same Issue
- Single-crystal neutron diffraction of urea-phosphoric acid: evidence for H-atom migration in a short hydrogen bond between 150 K and 350 K
- Determination, prediction, and understanding of structures, using the energy landscapes of chemical systems - Part I
- Hydrogen bond network of the layered phosphates γ-Zr(H2PO4)(PO4)⋅2H2O and γ-Hf(H2PO4)(PO4)⋅2H2O determined by neutron powder diffraction
- Structural phase transition of GdGa2 at high pressure
- Absorption spectra of calcium tartaric and cadmium oxalate crystals, grown in gel and doped by chromium, cobalt and nickel
- Elastic and thermoelastic properties of selected organic crystals: acenaphthene, trans-azobenzene, benzophenone, tolane, trans-stilbene, dibenzyl, diphenyl sulfone, 2,2´-biphenol, urea, melamine, hexogen, succinimide, pentaerythritol, urotropine, malonic acid, dimethyl malonic acid, maleic acid, hippuric acid, aluminium acetylacetonate, iron acetylacetonate, and tetraphenyl silicon
- Structure and ferroelasticity of tetramethylammonium-hexafluoroosmate(IV), (TMA)2[OsF6]
