Biological oxidation of hydrocarbons

Biological oxidation of hydrocarbons is a commonly observed process. 

Thus, as in the case of alkenes in the preceding chapter, we start with the radical type of activation that is much older. Transition-metal compounds play a key role in radical activation, because they provide very strong oxidants that can oxidize hydrocarbons either by (reversible) electron transfer or H-atom transfer (more rarely by hydride transfer). Biological oxidation of hydrocarbons involves reactive metal-0X0 species in methane mono-oxygenases and many related synthetic models, and a number of simple metal-oxo complexes also work. The clear criterion of distinction between an organometallic C-H activation and a radical activation is the above selectivity in activated C-H bonds. 

The second proposal is a bit more imaginative and arises from the above arguments that 0—0 bond homolysis is much too slow to be involved in oxidations by peroxynitrate. Pryor and coworkers invoked the intermediacy of a metastable form of peroxynitrous acid (HO—ONO ) in equilibrium with its ground state. This so-called excited state of peroxynitrous acid has, to date, eluded detection or characterization by the experimental community. However, recent high-level theoretical calculations by Bach and his collaborators have presented plausible evidence for the intermediacy of such a shortlived species with a highly elongated 0—0 bond and have confirmed its involvement in the oxidation of hydrocarbons (see below). The discovery of this novel series of biologically important oxidants has fostered a new area of research in both the experimental and theoretical communities. In this chapter we will describe many of the more pertinent theoretical studies on both the physical properties and chemical reactivity of peroxynitrous acid. 

The current views about aerobic biological oxidation of alkanes and arenes involving various oxygenases. Its chemical simulations are discussed in this chapter, which gives only a brief survey of the most recent data for biological C-H activation and hydrocarbon oxidation. It is noteworthy that, somewhat unexpectedly, important and profound analogies exist between chemical activation by metal complexes and biological C-H oxidation. It is necessary to note that many books [14] and reviews [15] have been devoted to enzymatic oxidations and processes that more or less closely model these oxidations. 

It should be noted that at present along with the molecular mechanism of peroxidation of lipids based on the theory of the liquid phase oxidation of hydrocarbons,77 there exists the concept of a relay model of peroxidation of lipids of biological membrane,76 which is more like the description of the oxidation processes of solid polymers. 

Biological oxidation of the hydrocarbon adamantane by the fungus Absidia glauca gives a mixture of two alcohols. Classify the carbon in adamantane that is oxidized in forming the major product. 

Katz, M., Chan, C., Tosine, H., Sakuma, T. (1979) Relative rates of photochemical and biological oxidation (in vitro) of polynuclear aromatic hydrocarbons. In Polynuclear Aromatic Hydrocarbons. Jones, P.W., Leher, P., Eds., pp. 171-189, Ann Arbor Science Publishers, Ann Arbor, MI. 

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