Oxidation of Benzene by N2O, the Panov Reaction

The catalytic oxidation of benzene to phenol in iron-containing zeolites is known as the Panov reaction The ZSM-5 zeolitic system is the preferred matrix. There are several ways in which the catalyst can be activated for this reaction. 

It is now well established that the active component of the catalytic reaction is monomeric Fe +. The Panov reaction consists of two reaction steps  

The imiqueness of the ZSM-5 catalyst relates to its stabilization of Fe + cations in the selected (a) sites of the zeohte ndcropores. There is increasing evidence that non-lattice alumina plays a promoting role, by potentially enhancing the relative stabUily of isolated Fe + centersl l. 

As a prehminaiy to our later comparison with biochemical systems (see Chapter 7), it is relevant to note here that the enzyme cytochrome P-450 also contains a single Fe center attached to a porphyrin stem. Cytochrome P-450 catalyzes the reaction of methane to methanol. There is also an enzyme that contains a two-iron cationic center that catalyzes the same reaction. In the methane monooxygenase enzyme, two Fe cations are bridged by oxygen and charge compensated by glutamate and histidine groupsl l. 

An important difference between the benzene oxidation reaction and methane activation, is the absence of an isotope effect in the benzene oxidation reaction. In the enzyme, CH4 activation is initiated by hydrogen abstraction. This initiates a radical-type reaction. Benzene oxidation in the Panov stem, however, follows a very different reaction path. 

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