Hydrogen bonds/bonding characterized

Hydrogen bonding descriptors, in particular, the ability of an atom in a given environment to be a donor Hd) and acceptor Ha) of a hydrogen bond characterized by the Abraham s constants. " ... 

The cyclic ACN dimer is formed thanks to two weak C—H- -N hydrogen bonds characterized by N- -H bond lengths of 2.633 A and a bond angle of 137.6°. They are manifested spectroscopically by the appearance of two far-IR bands N) and... 

V -( a2-OH)2-V motifs, linked by tJ.2-S04, are significantly twisted with respect to each other resulting in the zigzag feature of the chain. The structure exhibits intrachain hydrogen bondings characterized by short 0(2A).H-(0) (1.895- 1.953 A). 

Ayotte P, Bailey C G, Weddle G FI and Johnson M A 1998 Vibrational spectroscopy of small Br (Fl20) and I Fl20) clusters infrared characterization of the ionic hydrogen bond J. Phys. Chem. A 102 3067-71... 

The infrared spectra of A-4-thiazoline-2-ones are characterized by a strong absorption around 1650 cm (55, 86, 103, 107. 870). For the N-H derivatives, the whole range 2700 to 3200 cm is covered by a strong absorption related to the dimeric and oligomeric states of the hydrogen-bonded structures (85, 86). 

V Hel IX (Section 27 19) One type of protein secondary struc ture It IS a right handed helix characterized by hydrogen bonds between NH and C=0 groups It contains approxi mately 3 6 amino acids per turn... 

This experiment describes a characterization analysis in which the degree of association, equilibrium constant, and hydrogen bond energy are measured for benzyl alcohol and phenol in CCI4. 

BW Beck, Q Xie, T Ichiye. Computational study of S—H S hydrogen bonds m [4Ee-4S]-type ferredoxm x-ray and NMR structures Characterization and implications for redox potentials. Protein Sci, submitted. 

Solvent effects on chemical equilibria and reactions have been an important issue in physical organic chemistry. Several empirical relationships have been proposed to characterize systematically the various types of properties in protic and aprotic solvents. One of the simplest models is the continuum reaction field characterized by the dielectric constant, e, of the solvent, which is still widely used. Taft and coworkers [30] presented more sophisticated solvent parameters that can take solute-solvent hydrogen bonding and polarity into account. Although this parameter has been successfully applied to rationalize experimentally observed solvent effects, it seems still far from satisfactory to interpret solvent effects on the basis of microscopic infomation of the solute-solvent interaction and solvation free energy. 

Only a limited number of coal-denved pitches were examined by H NMR because of their low solubility in solvents commonly used m conventional proton magnetic resonance. Table 12 reports the distribution of hydrogen for three of the pitches. Unlike coal-tar pitches, which typically have over 85% of the hydrogen bonded to aromatic carbon, the matenals listed in Table 12 are characterized by a high content of aliphatic hydrogen. 

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