Oxidative Cleavage of Alcohols: Oxygen Effects

Oxidation of p -substituted phenyl- tert -butylcarbinols with chromic acid gives data which correlates well with the Hammett relationship and cleavage yields as high as 60%. Manganous ion reduced both cleavage and the deuterium isotope effect. p -Substituents appear to have no effect on cleavage ratios. An induced air oxidation step has been detected during Cr(VI) oxidations of cleavable alcohols at high cleavage conditions. This step, however, is not responsible for the cleavage reaction. Oxidation yields are higher in the presence of oxygen, but the rates are lower. When phenyl- tert -butylcarbinol and p -anisyl- tert -butylcarbinol react with Fenton's Reagent, cleavages greater than those with chromic acid are obtained. Ce(IV) cleaves these carbinols almost quantitatively.