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Geometry of hydrogen bonds

Many studies have been made of the geometry of hydrogen bonds, and the evidence shows that in most (though not all) cases the hydrogen is on or near the... [Pg.99]

The discussions of Sects. 3.1,3.2 and 3.3 are structured by reference to a set of rules that were proposed some years ago [103,104] for rationalising the angular geometries of hydrogen-bonded complexes of the type B- -HX, where X is a halogen atom. These rules are as follows ... [Pg.34]

Compare the flexibility of the geometry of hydrogen-bonding to the non-bonding electron-pairs of neutral oxygen elicited by the demands of crystal forces (Donohue, 1968)... [Pg.206]

H.A. Staab, T. Saupe, Proton sponges and the geometry of hydrogen bonds aromatic nitrogen bases with exceptional basicities. Angew. Chem. Int. Ed. Engl. 27, 865-1008 (1988)... [Pg.384]

The geometry of the hydrogen bond can be described by the parameters R, n, r2, and 0, as shown in Fig. 11.2.1. Numerous experimental studies have established the following generalizations about the geometry of hydrogen bonds ... [Pg.403]

Given the standard geometries of hydrogen-bonded atoms, or of helices and sheets, it is possible to apply pattern-recognition techniques to analyze the conformation of a protein. This has been done (many times) and is a useful approach to the extent that the problem is well-defined. However, in many cases helices deviate from standard geometry — especially at the ends where they can tighten up or unravel. Any investigation that requires analysis of this kind of detail is better pursued interactively. [Pg.157]

The problem of transference from the hydrogen bonds in the crystal to those in a biological process is not different, in principle, from the transference of molecular structural information determined by crystal structure analysis to the interpretation of the mechanism of a chemical reaction. In Chapter 4, we discuss the differences between the geometry of hydrogen bonds in crystals and in the free molecule models that are necessarily used by the theoretical methods. [Pg.14]

Pedersen B (1974) The geometry of hydrogen bonds from donor water molecules. Acta Cryst B30 289—291... [Pg.512]

Jeffrey GA, Maluszynska H (1986) A survey of the geometry of hydrogen bonding in barbiturates, purines and pyrimidines. J Molec Struct 147 127-142... [Pg.513]

The geometries of hydrogen bonded trimers and tetramers in solid 3,5-sub-stituted pyrazoles (Fig. 6) have been studied from consideration of both 15N chemical shift tensors and dipolar interactions involving 15N [122]. [Pg.23]

The question of the exact geometry of hydrogen bonds (distances, angles, lone-pair directionality) has been reviewed [194]. [Pg.16]

Proton sponges derived from N-heteroaromatic bases, geometry of hydrogen bonds 99AG(E)865. [Pg.48]

In this study, we have chosen the supermolecule approach and have used the semi-empirical quantum mechanical method called PCILO (Perturbative Configuration Interaction using Localized Orbitals) (16) to calculate intermolecular interactions. This method has recently been used successfully to calculate the intermolecular energies and geometries of hydrogen-bonded dimers of hydrocarbons and water (17,18). H-bonded complexes are particularly well characterized by this method (19). [Pg.243]

Flere, /(AR, Aa) is a scaling function penalizing deviations from the ideal geometry of hydrogen bonds and ionic interactions, Nrot is the number of... [Pg.353]

In model systems used to study Type B PCET reactions, the PCET complex is provided by self-assembly, which entails the noncovalent interaction of two or more molecular subunits to form a complex structure whose properties are determined by the nature and positioning of the molecular components [85-91]. The strengths and geometries of hydrogen bonds through which ET occurs can profoundly affect the PCET kinetics [92, 93]. [Pg.523]

This interaction, which does not depend on the orientation of the molecule with respect to the external magnetic field, gives valuable information on the local structure, such as for example the bond strength and geometry of hydrogen bonds to the radical or on the covalency of metal ligand bonds. [Pg.170]


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See also in sourсe #XX -- [ Pg.139 ]




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