Perhalate ions

The hydrates of perchloric acid exist in at least six crystalline forms. The monohydrate is composed of H30+ and CIO4 connected by hydrogen bonds. All perhalate ions XO4 are tetrahedral, with 7h symmetry, as shown below ... 

Finally, we must consider the possibility of production of perhalate ions by disproportionation of the halate ions. Since the acids H0X02 and HOXO3 are all strong, these equilibria are independent of pH. The reaction... 

Molecular halogen, halide, halate, and perhalate ions. The exchange rate between hahde ions and molecular halogens, namely Cl and CI2, Br and Br2 and also I and I2, in aqueous solutions is too large to be measured by an ordinary radiochemical method. 

Covalent compounds with the halogen nucleus at a site of tetrahedral or octahedral symmetry, as in CIO4 or IF5, present a low EFC at the halogen nucleus and frequently have relatively sharp resonances. Indeed the spectra of the tetrahedral perhalate ions in acetonitrile solution show exceptionally sharp lines that enable secondary isotope effects on shielding to be observed. The shielding difference between (CT 04) and (CT O Os)" is 0.090 ppm. 

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