Oxidation branched alkanes

The degradation of squalene by Marinobacter sp. strain 2sq31 (Rontani et al. 2002) is initiated by oxidative fission, although the subsequent steps are carried out by ()-oxidation and carboxylation that are comparable to those used for branched alkanes. 

Pirnik MP (1977) Microbial oxidation of methyl branched alkanes. Crit Rev Microbiol 5 413-422. 

The photo-oxidation of a solid branched alkane can be expected to proceed in localized domains, new oxidation chains being generated from the photo-cleavage of -00H products, and chain propagation (reactions 2 and 3) being concentrated close to each initial site in a given domain to produce a zone of high -00H concentration. Thus the distribution of an additive in and around these domains is of special importance. 

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

Rust [55] studied the oxidation of branched alkanes and was the first to observe the formation of dihydroperoxides as primary products of the hydrocarbon oxidation [55], Dihydroperoxide was found to be the main product of 2,4-dimethylpentane oxidation by dioxygen at 388 K ... 

The peculiarities of the oxidation of PP, whose molecules have alternating tertiary C—H bonds in the (3-position, are of special interest. Such branched alkanes are oxidized with the formation of polyatomic hydroperoxides produced by the intramolecular isomerization of the peroxyl radical [88],... 

The oxyfunctionalization of alkanes with H2O2 on TS-1 has only been reported very recently [113-114]. Linear or branched alkanes are oxidized to secondary and/or tertiary alcohols and ketones, the latter ones being formed by consecutive oxidation of the secondary alcohols. Primary alcohols are not detected. At 50°C maximum turn-overs of n-hexane of 35 mol/mol Ti were reported... 

Iodine(III) tnfluoroacetates (iodine tristrifluoroacetate and lodosobenzene bis-trifluoroacetate) resemble lead(IV), thallium(III) and mercury(II) reagents in their reactions but do not share the undesirable high toxicity typical for the heavy metals Iodine tristrifluoroacetate is a very powerful oxidant that can introduce the trifluoroacetoxy group even into alkanes [60 61] Because branched alkanes react ... 

Incorporating redox catalytic sites within a zeolite lattice framework should also provide a basis for effecting shape selective oxidations. Indeed, it has recently been reported67 that TS-1 catalyzes the shape selective oxidation of alkanes with 30% H202. Linear alkanes were oxidized much faster than branched or cyclic alkanes, presumably as a result of the molecular sieving action of TS-i. The products were the corresponding alcohols and ketones formed by oxidation at the 2- and 3-positions, e.g.,... 

Air oxidation of /i-butane to maleic anhydride is possible over vanadium phos(4tate and, remaiicably, a 60% selectivity is obtained at 85% conversion. In the gas phase oxidation, in conffast to the situation found in the liquid, n-allcanes are oxidized more rapidly than branched chain alkanes. This is because secondary radicals are more readily able to sustain a chain for branched alkanes the relatively stable tertiary radical is preferentially formed but fails to continue the chain process. Vanadium(V)/ manganese(II)/AcOH has been used as a catalyst for the autoxidation of cyclohexane to adipic acid, giving 25-30% yields after only 4 h. ... 

The oxidation of a branched C4 alkane, isobutane, was carried out to probe the mechanism of the C-H bond activation of alkanes on the VPO catalysts [103]. Maleic anhydride was among the products of oxidation of this branched alkane. In the case of isobutane 29 (Figure 15), the surface-bound peroxo radical would show discrimination in activating first the weaker tertiary C-H bond. The... 

Appropriate modification of the ESR spectrometer and generation of free radicals by flash photolysis enables time-resolved (TR) ESR spectroscopy [22]. Spectra observed under these conditions are remarkable for their signal directions and intensities. They can be enhanced as much as one-hundredfold and appear as absorption, emission, or a combination of both. Effects of this type are a result of chemically induced dynamic electron polarization (CIDEP) these spectra indicate the intermediacy of radicals whose sublevel populations deviate substantially from equilibrium populations. Significantly, the splitting pattern characteristic of the spin-density distribution of the intermediate remains unaffected thus, the CIDEP enhancement not only facilitates the detection of short-lived radicals at low concentrations, but also aids their identification. Time-resolved ESR techniques cannot be expected to be of much use for electron-transfer reactions from alkanes, because their oxidation potentials are prohibitively high. Even branched alkanes have oxidation potentials well above the excited-state reduction potential of typical photo-... 

Similar to linear and branched alkanes, cycloalkanes also give rise to radical cations in zeolites, spontaneously or upon y-radiolysis. This brief discussion of selected examples is intended only to give a flavor of the work being done. Thus, a 13-line radical cation spectrum (a = 0.17 mT, g = 2.003) obtained upon incorporation of 1-methylcyclohexane, 43, into zeolites [71] was identified as 1,2-dimethylcyclopentene radical cation, 44 + (two sets of protons with hyperfine couphng constants in the ratio of ca 2 1 a = 1.67 mT, 2 CH3 a = 3.42 mT, 4H) [72]. The formation of 44 + was rationalized by protonation of the 3° carbon of 43, followed by loss of H2. Loss of a proton from a rearranged carbocation may generate 44, which is oxidized to 44 + by a Lewis site. 

A brief introduction to the oxidation of oxygenated compounds is appropriate as they are important intermediates in the total oxidation of an alkane through to CO2 + H2O. In the temperature region below 1000 K, the major oxygenated species are aldehydes (ketones from highly branched alkanes) and O-heterocyclic compounds formed via RO2 QOOH iso-merizations. An impression of the relative activity of oxiranes and oxetanes... 

Aliphatic EC>8-EC16 Fraction. Hydrocarbons in this fraction are oxidatively metabolized to fatty acids and alcohols, apparently mediated by cytochrome P-450 isozymes (see Miller et al. 1996 for review). Studies regarding the metabolism of hydrocarbons in this fraction in humans or animals provide suggestive evidence that metabolism may be slow. In a study of humans exposed to 100 ppm white spirit 6 hours/day for 5 days (white spirit is a mixture comprised predominately of C10-C12 linear and branched alkanes), only minor differences were observed in the GC-MS spectrum of hydrocarbons in biopsied fatty tissue, than in the spectrum of hydrocarbons in the test material (Pedersen et al. 

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