In the series of reagents used in heterogeneous oxidation reactions, active manganese dioxide has acquired a prominent place among such oxidants as copper oxide, mercury(II) oxide, silver oxide, lead dioxide, sodium bismuthate, 1–3 nickel peroxide, 4, 5 manganese(III) acetate, 6, 7 silver carbonate on Celite, 8 seloxcette9 (chromic anhydride intercalated in graphite), and the recently introduced potassium permanganate on molecular sieves10 and barium manganate (BaMnO4).11, 12 The last two reagents10, 11 may be efficient oxidants for the conversion of alcohols into carbonyl compounds (under mild conditions).

The Oxidation of Organic Compounds by Active Manganese Dioxide

Excess oxygen of chromia: II. Reaction with diphenylpicrylhydrazine

Surface active sites for dehydrogenation reaction of isopropanol on manganese dioxide

The reaction between a hydroquinone aqueous solution and manganese dioxide has been investigated by electron paramagnetic resonance spectroscopy. A very stable p-benzosemiquinone anion is formed when an aqueous solution of hydroquinone is passed through a column of manganese dioxide. The kinetics for the reaction between hydroquinone and manganese dioxide follow the equation 






where A0 is the initial concentration of hydroquinone, C is the concentration of p-benzosemiquinone anions, W is the amount of manganese dioxide, F is the feed rate of a hydroquinone aqueous solution, and k10 and k20 are constants; k10 = 3.1 × 10−2 (cm3/g MnO2· min), k20 = 3.2 (cm3/g MnO2·min).



A mechanism for the reaction is proposed such that Mn(IV) in manganese dioxide is reduced to Mn(II) with hydroquinone from which the semiquinone anion is formed via a neutral semiquinone. The formation of semiquinone anions from several substituted hydroquinones is also discussed.

ESR studies on the formation of p‐benzosemiquinone anions over manganese dioxide

Adsorption of 1,1-diphenyl-2-picrylhydrazyl on rutile: The role of moisture and orientation

The surface reaction between manganese dioxide and 1,1-diphenyl-2-picrylhydrazine. Two type EPR methods for the estimation of active surface areas of oxides

A.T.T. Oei

Papers

The surface reaction between manganese dioxide and 1,1-diphenyl-2-picrylhydrazine. Two type EPR methods for the estimation of active surface areas of oxides