Results 171 to 180 of about 272 (215)

Symmetrically bifurcate hydrogen bonding—IV

Tetrahedron, 1973
Abstract The effect of the size and branching of alkyl substituents R1 and R2 on the formation of all possible stereoisomers of bis(β-acylvinyl)amines, [R1COCR2CH]2NH, has been investigated. IR and NMR data show that steric requirements of these substituents and resonance stabilization of the s-trans system are the main factors determining the ...
J. Dabrowski, Z. Swistun
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Hydrogen-bond symmetrization and molecular dissociation in hydrogen halids

Physica B: Condensed Matter, 1999
Abstract Hydrogen chloride is a simple diatomic molecule forming a planar zig-zag chain of molecules connected by hydrogen bonds in the solid phase. Raman spectra were measured for solid HCl to 60 GPa at room temperature. The molecular stretching frequency falls toward zero at about 51 GPa, where the molecular vibrational peaks disappear and the ...
K Aoki, E Katoh, H Yamawaki, M Sakashita, H Fujihisa   +4 more
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Effect of pressure on the symmetric hydrogen bond in (CCI3COO)2HK

Physica Status Solidi (a), 1988
The effects of pressure and temperature on the NQR spectrum of (CCl3COO)2HK crystals are studied. The measured temperature dependences of the NQR spin-lattice relaxation time and NQR frequency prove the symmetry of the hydrogen bond. Some pressure induced polymorphic phase transitions are observed.
M . Mackowiak, P. Koziol
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Strong and symmetric hydrogen bonding in the hydrogen di-superoxide anion

Chemical Physics Letters, 2000
Abstract The structure of the triplet state of the hydrogen di-superoxide anion, [O 2 –H–O 2 ] − , has been investigated by ab initio quantum chemical geometry optimizations. The anion has two short hydrogen bonds that are symmetry connected. At the highest level of theory considered (B3LYP/AUC-cc-pVTZ) the O–O bond length is 1.332 A, the hydrogen ...
S.J Knak Jensen, I.G Csizmadia
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Molecular orbital studies of hydrogen bonds. VIII. Malonaldehyde and symmetric hydrogen bonding in neutral species

Journal of the American Chemical Society, 1975
Alan D. Isaacson, Keiji Morokuma
exaly   +2 more sources

Pressure-Induced Hydrogen Bond Symmetrization in Babingtonite

Inorganic Chemistry
Hydrogen bond symmetrization and electronic spin transition of iron under pressure are key factors in understanding the physical properties and behaviors of Fe- and H-bearing minerals. However, the coexistence of these two effects may often result in inconsistent interpretations.
Yungui Liu, Xiang Li, Cheng Qian, Susanne Müller, Katarzyna Skrzyńska, Samuel Gallego-Parra, Gaston Garbarino, Aleksandr Chumakov, Ilya Kupenko, Xiang Wu   +9 more
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A symmetrical bridged hydrogen bond in organic compounds

Journal of Molecular Structure: THEOCHEM, 1983
Abstract Calculations by both ab initio (STO-3G) and MINDO/3 methods have been carried out for the ions (H n X·H·XH n ) m (X = B, C, N, 0, F, Si, P, S and Cl; n = 1, 2, 3; m = ±1) and (HYCH 2 CH 2 CH 2 Y) m (Y = CH 2 , NH 2 , NH, O, F; m = ±1). Fully optimized geometries have been obtained for all species. The orbital nature of a bridging
Ruslan M. Minyaev, Vladimir I. Pavlov
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A lithium ethylenediphosphonate containing lithium chains and symmetric hydrogen bonds

Acta Crystallographica Section C Crystal Structure Communications, 2006
In the title compound, catena-poly[lithium-μ 3 -ethylenediphosphonato], [Li(C 2 H 7 O 6 P 2 )] n , the supramolecular monoclinic (C2/c) structure consists of one-dimensional lithium chains [Li···Li = 2.7036 (8) A] that are embedded within ethylenediphosphonate anions linked by strong symmetric hydrogen bonds [O···O = 2.473 (3) A].
Ching Yuan, Cheng, Kuan Jiuh, Lin
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Short Intramolecular Hydrogen Bonds: Derivatives of Malonaldehyde with Symmetrical Substituents

Journal of the American Chemical Society, 2008
A systematic study of various derivatives of malonaldehyde has been carried out to explore very short hydrogen bonds (r(OO) < 2.450 A). Various electron-withdrawing groups, including CN, NO(2), and BH(2), have been attached to the central carbon atom, C(2).
Jacqueline C, Hargis, Francesco A, Evangelista, Justin B, Ingels, Henry F, Schaefer   +3 more
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Symmetric versus asymmetric hydrogen bonds in polymeric water

Chemical Physics Letters, 1969
Abstract The stability of symmetric and asymmetric hydrogen bonds in condensed ring structures of polymeric H2O was compared in the CNDO/2 method. In a six-membered ring the asymmetric structure is much more stable, but in condensed ring systems the difference between the two becomes smaller.
exaly   +2 more sources