OH - -O Hydrogen Bonds in the Ices and High Hydrates

The many polymorphs of ice [422, 423] and the wide variety of ice-like hydrate inclusion compounds provide a source of information about 0H---0 hydrogen bonds where the water molecules are the structure-determining molecular species 

Metrical Aspects of Tlvo-Center Hydrogen Bonds 

It is noticeable that the monosaccharides, which are oblate molecules able to pack efficiently, form significantly less hydrates than do the disaccharides or nucleosides, which are more awkward-shaped molecules from the packing point of view. 

These hydrogen-bond distances in ice provide a useful standard with which to compare the range of O-H- -O distances observed in other types of crystal structures. For example when water molecules accept hydrogen bonds from the carboxylic acid -OH donors, i.e., 0=C0H- -OwH2, the bonds are stronger than in ice. In the reverse situation, when the OH donors of the water molecules bond to carboxylic acid C=0 acceptors, the bonds are significantly Weaker (see Thble 7.5). 

Unfortunately, none of the hydrate inclusion compounds which have less regular structures, such as the tetrabutyl and isoamylammonium salt hydrates [432] and the amine semi-clathrates [433, 434], has been studied by neutron dif- 

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