Alkane functionalization metal-free

Now that the a/3-diadsorbed species is known to be tr-complexed olefin, the simplest interpretation of rollover is that the metal-olefin bond breaks the free olefin has then a transient existence in the gas phase and can migrate from one type of site to another. That this occurs to an appreciable extent even at ambient temperatures starting with alkane in excess D2 may seem surprising but is powerful support for the olefin migration step postulated in hydrocracking and hydroreforming on dual-functional catalysts. 

In this chapter, two new approaches for the synthesis of metal-polymer nanocomposite materials have been described. The first method allows the preparation of contact-free dispersions of passivated gold clusters in polystyrene, and it is based on a traditional technique for the colloidal gold synthesis—that is, the alcoholic reduction of tetrachloroauric acid in presence of poly(vinyl pyrrolidone) as polymeric stabilizer. The primary function of the stabilizer is to avoid cluster sintering, but it also allows us to isolate clusters by co-precipitation. It has been found that the obtained polymer-protected nanometric gold particles can be dissolved in alkane-thiol alcoholic solutions to yield thiol-derivatized gold clusters by thiol absorbtion on the metal surface. Differently from other approaches for thioaurite synthesis available in the literature, this method allows complete control over the passivated gold cluster structure since a number of thiol molecules can be equivalently used and the... 

The mechanistic details involved in these reactions remain obscure. However, the limited amount of available evidence suggests that a mixed function oxidase is responsible for the conversion of alkanes to secondary alcohols in B. oleracea. The O2 requirement for the conversion of exogenous [G- H]nonacosane to both secondary alcohols and ketones (Kolattukudy et al., 1973a ), as well as the incorporation of from O2 in the ketone (Kolattukudy, 1970a), support this hypothesis. Furthermore, this conversion was inhibited by metal ion chelators such as phenanthroline, and this inhibition was reversed by Fe ". In any case, without a cell-free preparation catalyzing the hydroxylation of hydrocarbons, the components involved in this reaction and the mechanistic details cannot be elucidated. 

In addition to the wide range of metal oxide catalysts that can cany out oxidation via redox catalysis, there are a host of other materials that can carry out oxidation over non-reducible metal oxides. The oxidation mechanisms over non-reducible metal oxides are quite different and typically involve the production of free radical intermediates. The mechanisms tend to contain both heterogeneous and homogeneous activation and functionality. The oxide is used to activate a free radical process that can then proceed in the gas phase or at the surface. Li-substituted MgO and the rare earth metal oxides are two classes of materials that are considered non-reducible oxidation catalysts. Here we wiU specifically focus on the activation of alkanes over non-reducible metal oxides. 

SWCNTs-porphyrin nanosensors have been fabricated for monitoring toxic substances in the enviromnent [215], Free-base, Ru and Fe octaethyl-and tetraphenyl-substituted porphyrins provided good selectivity and sensitivity to various VOCs tested (acetone, butanone, methanol, ethanol). Nonco-valently functionalized SWCNTs with iron tetraphenylporphyrin were used for benzene detection [216], SWCNTs noncovalently functionalized with copper phthalocyanine and free-base porphyrins were used as sensing layers for the detection of toluene [217]. Also, MWCNTs were used as sensors for benzene, toluene, and xylene, when fnnctionalized with metal tetraphenyl porphyrins [218], SWCNTs-poly(tetraphenylporphyrin) hybrid was prepared and tested as a low-power chemiresistor sensor for acetone vapor [219]. A chemiresistive sensor array was fabricated from SWCNTs noncovalently functionalized with metallo mcxo-tetraphenylporphyrins (Cr(III), Mn(III), Fe(III), Co(III), Co(n), Ni(n), Cu(II), and Zn(II)) [220]. Its responses were treated by statistical analyses and allowed to classify VOCs into five classes alkanes, aromatics, ketones, alcohols, amines. Amines detection as an indicator of meat spoilage was achieved by the same group with the same sensor array [221]. 

High oxidation state transition-metal oxide ions isolated and sparsely distributed within the Al + sublattice of open-structure metal microporous alumino-phosphate (MAlPOs) solids (M = Co +, Mn +, Fe +) function as powerful redox, catalytically active centers in the selective oxyfunctionalization of alkanes. Important chemical commodities are also conveniently prepared by using such microporous catalysts in solvent free conditions, and using oxygen or air as oxidants [179,180]. 

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