Periodate oxidations glycol cleavage mechanisms

Lead tetraacetate is an alternative to periodate for glycol cleavage. It is particularly useful for glycols that have low solubility in the aqueous media used for periodate reactions. A cyclic mechanism is indicated by the same kind of stereochemistry-reactivity relationships discussed for periodate. Unlike periodate, however, glycols that cannot form cyclic intermediates are eventually oxidized. For... 

The mechanism of 1,2-cleavage of glycols with sodium bismuthate is generally considered to be similar to that with lead tetraacetate and periodic acid [40CB563], although there is still some controversy [50JCS(C)1907]. A cyclic bismuthate diester is postulated as a plausible intermediate, though the rates of oxidation observed are not so different between cis- and trans-, 2-cyclohexanediols. 

Periodic acid also cleaves carbon-carbon bonds of a-hydroxyketones and a-hydroxyaldehydes by a similar mechanism. Following are abbreviated structural formulas for these functional groups and the products of their oxidative cleavage by periodic acid. As a way to help you understand how each set of products is formed, each carbonyl in a starting material is shown as a hydrated intermediate that is then oxidized. In this way, each oxidation can be viewed as being analogous to the oxidation of a glycol. 

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