Permanganates with onium cations, soluble in non-polar and little polar organic solvents, make it possible to oxidize substrates which are insoluble in water. Permanganate is reduced in these media like in neutral aqueous solutions. In contrast to older views, the main intermediate in these reactions is Mn(IV) in the form of colloidal MnO₂. The catalytic effect of this intermediate is associated with its large surface on which the reactants are adsorbed. Many oxidation reactions with solubilized permanganate exhibit an autocatalytic mechanism.