Hydrogen bonding in crystal structures

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. 

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 ... 

Jeffrey GA (1989) Hydrogen bonding in crystal structures of nucleic acid components purines, pyrimidines, nucleosides and nucleotides. In Saenger W (ed), Landolt-BOrnstein. Numerical Data and Functional Relationships in Science and Technology. New Series, Group VII, Vol. Ib. Springer, Berlin, pp 277-348... 

In some force fields, a special function is assigned to the interaction between the hydrogen atom and the acceptor atom in a hydrogen bond. Some force fields assume the interaction to be strictly Coulombic, whereas others add a special 10-12 function. In some cases a more complicated function that depends on the angles in the four-atom system —the acceptor antecedent, acceptor, hydrogen and donor heavy atom —has been attempted. However, a study of the amide hydrogen bond in crystal structures and, later, carboxylic acids demonstrated that such functional forms are not supported by the experimental data and thus led to the conclusion that weak A "H interactions (e.g., H 0, H N) are mainly electrostatic. ... 

Vinogradov, S.N. Hydrogen bonds in crystal structures of amino acids, peptides and related molecules, Int. J. Peptide Protein Res. 14(4) (1979) 281—289. 

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