Oxidation of alcohols in nonpolar media by permanganate ions intercalated into layered double hydroxide

The oxidation of alcohols with a layered double hydroxide(LDH), Mg2+-Al3+-MnO4-, was investigated. The interlayer MnO4- anions show the activity of oxidizing alcohols at room temperature in a nonpolar solvent such as benzene. The reaction proceeds selectively to afford the corresponding aldehyde or carboxylic acid depending on a starting alcohol. For instance, when the alcohol was benzyl alcohol, benzaldehyde was obtained predominantly even when a small quantity of the alcohol still remained in the reaction system. On the contrary, the oxidation of 1-octanol proceeds consecutively to give a carboxylic acid, while the alcohol remained sufficiently, with a reduced yield of 1-octanal. Adsorption of these alcohols and the corresponding aldehydes on the LDH was examined using benzene as a solvent. Adsorption amount of benzaldehyde was far smaller than that of benzyl alcohol, whereas there was little difference in the adsorption amounts of 1-octanol and 1-octanal. This low ability of benzaldehyde to adsorb on the LDH explains the selective oxidation of benzyl alcohol to yield benzaldehyde.