Mikito Kashima

The autoxidation of aromatic hydrocarbons catalyzed with cobaltic acetate in acetic acid solution: I. The oxidation of toluene

Abstract The kinetics of the oxidation of toluene catalyzed by cobaltic acetate in acetic acid have been studied at 60 °C. The oxidation proceeds without induction period, and the maximum absoiption rate of oxygen as well as the maximum reduction rate of cobaltic ion were observed at the beginning of the reaction. Eoth maximum rates can be expressed as follows, −d O 2 dt = k[φ- CH 3 ][ Co(III)] 2 [ Co(II) ] −1 −d Co(III) dt = k′[φ- CH 3 ][ Co(III) ] 2 [ Co(II) ] −1 with k′ k ~ 1.7 . The oxidation product was exclusively benzaldehyde at the early stage of oxidation. The following mechanisms are proposed: (1) The oxidation of toluene to benzyl radical proceeds by the reaction of toluene with a dimer of cobaltic ion; (2) Benzylperoxy radical is oxidized to benzaldehyde by a cobaltic ion.

Isotope effect of aromatic coupling reaction catalyzed by palladium acetate

Abstract Isotope effect in palladium catalyzed coupling reaction of aromatic compounds has been measured under oxygen pressure as well as under atmospheric pressure. For deuterobenzene, a large isotope effect ( k H k D ) was found to be 2.1–2.5 at 150 °C under oxygen pressure and to be 4.1–5.1 at room temperature under atmospheric pressure. On the basis of these isotope effects, we proposed the two-step hydrogen abstraction mechanism. Under oxygen pressure, oxygen plays an important role in the re-oxidation of reduced palladium(O) complex.