|MadSci Network: Chemistry|
Two different questions are being raised here: the oxidation of hydrogen peroxide by permanganate ion and manganese acting as a catalyst . For the first question we have to say that the decomposition of H2O2 is a redox reaction in which permangante acts as an oxidant, and it is consumed by changing its oxidation state from (VII) to (II), taking 5 electrons from the other substance involved in the reaction, the hydrogen peroxide. If the reaction takes place in a acidic media the products will be that Mn(II) specie (colourless and perfectly soluble in water) and oxygen gas. In neutral or basic media the oxidation is not cpmplete and produces not Mn(II) but Mn(IV) in the form of the oxide, MnO2  which precipitates as a brown solid. So permanganate does not act as a catalyst but as a reagent. That is on one side. But manganese can also act as a catalyst . Catalysts work by decreasing the activation energy of a chemical reaction, by forming an activated complex with a lower energy compared to that of the reagents by themselves, and being recovered to be used again and again as they are not consumed. This complex can be formed by bonding of the catalyst with the reagent (both as dissolved species, in homogenoeus media) or adsorption of the reagent on the surface of the catalyst (this is, a solid catalyst for heterogeneous catalysis). The changes on the electronic structure of the reagent-catalyst complex compared with the solo-reagent make the reaction with the other specie easier in energetic terms, or the catalyst bring the two species closer together, or the reaction happens on a supported surface... . Manganese is specially good at this. It can be found to work as a catalyst in Nature either by itself or, more commonly forming an organometallic complex, the chlorophil being the more popular. The fact that it is such a good catalyst and that it can easily form these complexes with organic fragments (ligands) which can have different structures or substituents, makes manganese the basis of many new and more specific catalyzers [4,5]. http://en.wikipedia.org/wiki/Permanganate; http://en.wikipedia.org/wiki/Manganese(IV)_oxide  http://en.wikipedia.org/wiki/Catalyst  Wei Li and S. Ted Oyama. J. Am. Chem. Soc., 1998, 120 (35), pp 9047–9052 Jiro Tsuji. "Transition Metal Reagents and Catalysts: Innovations in Organic Synthesis." John Wiley & Sons, Ltd. 2000. DIRK E. DE VOS, BERT F. SELS, AND PIERRE A. JACOBS; "ADVANCES IN CATALYSIS" VOL. 46. Academic Press. 2001.
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