Geometrical Features in Crystalline Compounds

The parameters of several thousand H bonds in many (and other) phosphorus compounds have now been determined by x-ray diffraction methods. Important general features which have anerged include the following  

When an H bond is formed between two atoms A and B, generally Ta + Tg (covalent) a-b (van der Waal) (Table 13.1) 

Accurate structural analyses confirm that the bonds are usually non-linear with O/H/O and N/H/0 angles within the range 140-180°. 

In the case of O-H-0 bonds, the donor P-OH linkage is invariably longer than the acceptor P-0 linkage which is frequently the phosphoryl P = O group, or part of an ionised POj group. 

Within the quoted range of O-H-0 distances above, most are 2.50 A. The remaining short H bonds are often placed in a special class. These bonds are stronger and 

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