Kinetics and mechanism of oxidation of aliphatic alcohols by oxone catalyzed by Keggin type 12-tungstocobaltate(II)

1626-1630The oxidation of various aliphatic alcohols by ox one catalyzed by Kegin type [CoIIW12O40]6- has been studied in a buffer medium of pH = 4. The reaction proceeds by the oxidation of [CoIIW12O40]6- to [CoIIIW12O40]5- by oxone which then oxidizes the alcohol in a rate  determining step generating alcohol free radical. The reaction is accelerated by increase in the pH of the solution due to the protonation equilibria of the oxidant. The reaction between oxone and [CoIIW12O40]6- has also studied and is found to proceed in two one-electron steps, involving formation HSO52-  free radical in a slow first step followed by its reaction with reductant in a fast step. The reaction rate is inhibited by the [H+] due to protonation equili bria of HSO5- which is the active species. Decreasing the relative permittivity of the medium increases the rate of the reaction which is attributed to the formation of an outer-sphere complex between the reactants. The activation parameters determined for both the reactions support the proposed mechanisms