Hydrogen bonds in crystals

The structures of the crystals cited. . . reveal the rather re markable fact that ordy in very exceptional cases does a hydro gen atom bonded to nitrogen or oxygen occupy a position such that hydrogen bond formation is impossible,  

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Many papers concerning the structural determination of hydrogen bonds in crystals were recently reviewed26. Hydrogen bonds are responsible for the self-assembling of... 

The largest number of hydrogen bonds in crystal structures of alkyl hydroperoxides refer to intermolecular bonds between the hydroperoxide proton and functionalities of the type 0=X, where X denotes a sulfur (e.g. 27), carbon (e.g. 30) or a phosphorous atom (e.g. 32, Figure 14, Table 7)93,108,115 geometry of [l,2-bis(diphenylphosphinoyl)ethane] bis(2,2-dihydroperoxypropane) (32) in the solid state is a rare example of a bifurcated hydrogen bond between an OOH donor and an 0=X proton acceptor. 

The second largest number of hydrogen bonds in crystal structures of alkyl hydroperoxides refers to interactions of the type OO—H OR R, where R is an alkyl group and R denotes H, alkyl or R O. The OO OR R distances vary between 2.67-2.91 A and the associated O—H O angles range from 152 to 177°. In some compounds, formation of intramolecular hydrogen bonds of the type OO—H 0=X would in principle have been feasible. The number of examples documented in the literature so far is clearly in favor of the intermolecular type of H bonding. 

A statisical analysis of x-ray crystallographic data has shown that most hydrogen bonds in crystals are nonlinear by about 10 to 15° Kroon Kanters van Duijneveldt-van de Rijdt van Duijneveldt Vliegenthart J. Mol Struct. 1975, 24, 109. See also Ceccarelli Jeffrey Taylor J,- Mol Struct. 1981, 70, 255 Taylor Kennard Versichel J. Am. Chem Soc. 1983, 105, 5761 1984,106, 244. 

IN RELATION TO BOND LENGTH IN HYDROGEN BONDS IN CRYSTALS... 

Energetics of hydrogen bonding in crystals. As an indication of the formation energy of a hydrogen bond, we counted the percentage of structures with... 

In an important paper, Braga, Grepioni, Desiraju and co-workers highlighted the abundance of C-H OC(M) hydrogen bonds in crystals of organometallic compounds [28b], The use of the CSD to analyse such hydrogen bonds across the series of d-block metals Ti-Ni led to a number of specific findings ... 

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. 

For hydrogen bonds in crystal structures, statistical analyses are possible only if neutron and X-ray data are combined. Tb obtain the metrical information described in this chapter, it is necessary to combine the limited amount of accurate neutron diffraction data with the much more abundant, but less accurate or reliable, data from the X-ray crystal structure analyses. This combination is possible if the X-H covalent-bond lengths, which appear notoriously shortened in the X-ray analyses, are normalized to standard neutron diffraction values. 

Table 10.2. IWo- and three-center C-H" 0 hydrogen bonds in crystal structures of nucleosides and nucleotides of the pyrimidine typea...

O-H O Hydrogen Bonding in Crystal Structures of Cyclic and Linear Oligoamyloses ... 

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