Periodate

Periodate (IPA: /pəˈraɪ.ədeɪt/) is an anion composed of iodine and oxygen. Periodates include two forms. The metaperiodate ion is IO₄⁻; the orthoperiodate ion is IO₆⁵⁻. Usually both forms are called periodates. Periodate is the conjugate base of periodic acid.

In neutral or weak acid conditions, IO₄⁻ is most common, in equilibrium with a smaller amount of H₄IO₆⁻. In basic conditions, H₃IO₆²⁻ is formed, plus some other ions.

Like its neighbor, tellurium, and unlike lighter halogens, iodine tends to be hexacoordinate, and the units H_nIO₆^(5−n)- are quite common; but tetracoordinate units, such as IO₄⁻, are also quite common with iodine, tetracoordinate being the only form possible with lighter perhalogenates, such as perchlorate.

Sodium metaperiodate can be isolated from the oxidation of sodium iodide with sodium hypochlorite and is best recrystallized from nitric acid. However, electrochemistry offers an easier alternative.

Uses

Periodates can cleave carbon-carbon bonds when both carbon atoms bear an oxygen atom, either in the form of a hydroxyl or a carbonyl group. This property is often utilized in molecular biochemistry for the purposes of modifying saccharide rings, as many five- and six-membered sugars often have vicinal diols.

Examples

• Potassium periodate, KIO₄
• Sodium periodate, NaIO₄

References