Oxidation alkane

An additional curious feature of alkylaromatic oxidation is that, under conditions where the initial attack involves electron transfer, the relative rate of attack on different alkyl groups attached to the same aromatic ring is quite different from that observed in alkane oxidation. For example, the oxidation of -cymene can lead to high yields of -isopropylbenzoic acid (2,205,297,298). 

Scheme 14 Biomimetic ligands used in iron-catalyzed alkane oxidation...

Scheme 17 Biomimetic ligands used in Fe-catalyzed alkane oxidations...

Alkane oxidation via a hydroperoxide was suggested many years ago, and seems to be operative in Acinetobacter sp. strain M-1 that has, in addition, a rather unusual range of substrates that include both n-alkanes and -alkenes. The purified enzyme contains FAD and requires copper for activity (Maeng et al. 1996). 

The operation of cytochrome P450 in alkane oxidation has been reported both in bacteria and in yeasts. It has been shown that alkane hydroxylases of CHYP 153 are widespread both in Gram-negative and Gram-positive bacteria that lack the integral membrane alkane hydroxylase (van Beilin et al. 2006). 

Grund A, J Shapiro, M Fennewald, P Bacha, J Leahy, K Markbreiter, M Nieder, M Toepfer (1975) Regulation of alkane oxidation in Pseudomonas putida. J Bacteriol 123 546-556. 

Hamamura N, CM Yeager, DJ Arp (2001) Two distinct monooxygenases for alkane oxidation in Nocardioides sp. strain CF8. Appl Environ Microbiol 67 4992-4998. 

Maeng JH, Y Sakai, Y Tani, N Kato (1996) isolation and characterization of a novel oxygenase that catalyzes the first step of -alkane oxidation in Acinetobacter sp. strain M-1. J Bacteriol 178 3695-3700. 

Parekh VR, RW Traxler, JM Sobek (1977) -alkane oxidation enzymes of a pseudomonad. Appl Environ Microbiol 33 881-884. 

TS-1 is a material that perfectly fits the definition of single-site catalyst discussed in the previous Section. It is an active and selective catalyst in a number of low-temperature oxidation reactions with aqueous H2O2 as the oxidant. Such reactions include phenol hydroxylation [9,17], olefin epoxida-tion [9,10,14,17,40], alkane oxidation [11,17,20], oxidation of ammonia to hydroxylamine [14,17,18], cyclohexanone ammoximation [8,17,18,41], conversion of secondary amines to dialkylhydroxylamines [8,17], and conversion of secondary alcohols to ketones [9,17], (see Fig. 1). Few oxidation reactions with ozone and oxygen as oxidants have been investigated. 

Theoretical studies of catalytic alkane-dehydrogenation reactions by [(PCP )IrH2], PCP rf-C6H3(CH2P112)2-l, 3 and [cpIr(PH3)(H)]+, suggest that they proceed through similar steps in both cases namely (i) alkane oxidation, (ii) dihydride reductive elimination, (iii) /3-II transfer from alkyl ligand to metal, (iv) elimination of olefin.402 The calculated barriers to steps (i), (ii), and (iv) are more balanced for the PCP system than for cp(PH3). 

Dihydroperoxides were found to be the primary products of branched alkanes oxidation. The intramolecular peroxyl radical reaction was proposed F. F. Rust [55]... 

The latest developments in the mechanistic understanding of platinum catalyzed alkane oxidation have involved Pt complexes with chelating ligands having mainly - but not exclusively - nitrogen donors. This review will focus on recent studies of these chelated Pt systems. The selection of the literature is somewhat subjective and will not be comprehensive. However, it should provide a true flavor of the current state of progress in the field. 

H202 selectivity (%) — (mol alkane oxidized/mol H202 converted) X 100. b Activity below detection limit. 

The streaking in the ED provides important evidence of the structural disorder attributed to the defects in (201) planes. This means that anions in (201) planes, located between vanadyl octahedra and phosphate tetrahedral, are involved in the alkane oxidation reaction. The disorder attributed to the catalyst anion loss is revealed only in (201) lattice planes, thus excluding all other planes in the crystal structure. 

Bredholt, H., Bruheim, P., Potocky, M. and Eimhjellen, K. (2002). Hydrophobi-city development, alkane oxidation, and crude-oil emulsification in a Rhodococcus species, Can. J. Microbiol., 48, 295-304. 

Heringa JW, Huybregtse R, Van Der Linden AC. 1961. -Alkane oxidation by a Pseudomonas formation and B-oxidation of intermediate fatty acids. Antonie Van Leeuwenhoef 27 51-58. 

Figure 1.3 Left. Detailed view of the Nb K-edge XANES data of a pyridine salt of niobium-exchanged molybdo(vanado)phosphoric acid (NbPMo fVJpry) as a function of temperature [31]. A change in niobium oxidation state, from Nb5+ to Nb4+, is identified between 350 and 420°C by a relative increase in absorption about 19.002 keV, and can be connected with the activation of the catalyst for light alkane oxidation. Right. Radial Fourier-transform EXAFS function for the NbPMo (V)pyr sample heated to 420°C [31 ]. The two peaks correspond to the Nb-O (1.5 A) and Nb-Mo (3 A) distances in the heteropolymolybdate fragments presumed to be the active phase for alkane oxidation. (Reproduced with permission from Elsevier.)...

Oxidation of unfunctionalized alkanes is notoriously difficult to perform selectively, because breaking of a C-H bond is required. Although oxidation is thermodynamically favourable, there are limited kinetic pathways for reaction to occur. For most alkanes, the hydrogens are not labile, and, as the carbon atom cannot expand its valence electron shell beyond eight electrons, there is no mechanism for electrophilic or nucleophilic substitution short of using extreme (superacid or superbase) conditions. Alkane oxidations are therefore normally radical processes, and thus difficult to control in terms of selectivity. Nonetheless, some oxidations of alkanes have been performed under supercritical conditions, although it is probable that these actually proceed via radical mechanisms. 

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