Alkanes oxidation with

Porphyrines and phthallocyanines suffer from oxidative degradation and oxidative dimerization [68]. The improved activity of the zeolitic systems is due to the effective site isolation within the pores, which prevents any bimolecular pathways to catalyst destruction [63]. Therefore, deactivation is more severe for the homogeneous catalysts than for the heterogenized TMPc. FePc itself is a poor catalyst for alkane oxidation with a high initial turn-over, but after less than 45 minutes it becomes completely inactive. On the contrary, FePc encaged in zeolite Y is stable for 24 hours [63]. 

Y. Ishii, S. Sakaguchi, A new strategy for alkane oxidation with O2 using N-hydroxyphthalimide (NHPI) as a radical catalyst, Catal. Surv. Jpn. 3 (1999) 27. 

Figure 4. Selectivity of alkane oxidation with Fe/Pd/A zeolite and H2/O2. a) substrate selectivity between n-octane and cyclohexane and b) regioselectivity of n-octane oxidation.

Y. Ishii, T. Iwahama, S. Sakaguchi, K. Nakayama, and Y. Nishiyama, Alkane Oxidation with... 

Scheme X.8 illustrates the proposed [53] mode of alkane oxidation with both peroxo and oxo groups bound to chromium(VI). This scheme also shows a possible way to regenerate an active Cr(Vl) species starting from Cr(lV).

Instead of the dioxygen-reductant pair, one can employ oxo componds containing an oxygen atom which is already partly reduced H2O2 [68], ROOH [69], PhIO [70], NaOCl [71], KHSO. [72], amine Af-oxides [73], and magnesium monoperoxyphtalate [74] (see also Chapter X). One of the most efficient (in terms of reaction rate and turnover number) systems is the combination of ruthenium porphyrin and 2,6-dichloropyridine A-oxide [73]. A simplified mechanism of alkane oxidation with iodosylbenzene catalyzed by iron porphyrinate is demonstrated in Scheme XI. 17. 

Scheme XL 17. The mechanism proposed for the alkane oxidation with iodosylbenzene catalyzed by iron porphyrinate.

Mechanism The reaction of and A -steroids with nitrosyl fluoride to form ni trimines is best discussed in conjunction with the nitrosyl chloride reaction leading tothe5a-chloro-6 -nitro steroids (33). Since nitroso alkanes are oxidized with nitrosyl chloride to nitro alkanes it is believed that 5a-chloro-6j5-nitro steroids are formed in this way from an initially formed 5a-chloro-6 -nitroso adduct. The same is true for nitrosyl fluoride up to the stage of the nitroso fluoride (56). Since NOF is a weaker oxidizing agent than NOCl the nitroso fluoride tautomerizes to the fluoro oxime (57) at a rate... 

Compound 123 (R = R = H) oxidatively adds chloroform and gem-dichloro-alkanes (940M4153). With methyl iodide, trans addition occurs and species 147 is formed. With dichloromethane, the route is three-fragment and four-electron, and the result is species 148 (R = H). Dichloromelhylbenzene and methyl dichloro-ethanoate give 148 (R = Ph and COOMe, respectively). Simultaneously, the... 

Nitrile oxides are usually prepared via halogenation and dehydrohalogenation of aldoximes [11] or via dehydration of primary nitro alkanes (Scheme 1) [12]. However, it is important to note that nitrile oxides are relatively unstable and are prone to dimerization or polymerization, especially upon heating. 1,3-Dipolar cycioaddition of a nitrile oxide with a suitable olefin generates an isoxazoline ring which is a versatile synthetic intermediate in that it provides easy access to y-amino alcohols, )5-hydroxy ketones, -hydroxy nitriles, unsaturated oximes, and a host of other multifunctional molecules (Scheme 1) [5a]. Particularly for the formation of )5-hydroxy ketones, nitrile oxide-olefin cycioaddition serve as an alternative to the Aldol reaction. 

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. 

Two main mechanisms may be proposed for the first step of the alkane interaction with platinum(II) complexes (1) oxidative addition... 

Moreover, the membrane could be mounted as an interface between the apolar substrate and the polar oxidant in a membrane reactor, avoiding the use of any solvent. Dilution of the reagents by solvent and competition between solvent and reagents on the active sites can thus be avoided. In the countercurrent membrane reactor, the substrate and the oxidant are circulated at each side of the membrane and alkanes can be oxidized with peroxides without solvents. Of course, the system carries all of the other advantages of membrane reactors continuous operation and easy separation. 

When cells are grown on non-aliphatic substrates, such as glucose, fructose, acetate, or glycerol, these are converted to appropriate precursors that can be incorporated into poly(3HAMCL)s via fatty acid synthesis. The resulting PHAs have a monomer composition that is similar to that seen after growth on alkanes, often with 3-hydroxydecanoic acid as the major monomer. ( -Oxidation does not seem to play a role in the conversion of these substrates into poly(3HAMCL) since the addition of a -oxidation inhibitor did not affect the monomer composition [47]. 

Aldehydes do not co-oxidize alkanes due to a huge difference in the reactivity of these two classes of organic compounds. Alkanes are almost inert to oxidation at room temperature and can be treated as inert solvents toward oxidized aldehydes [35]. Olefins and alkylaromatic hydrocarbons are co-oxidized with aldehydes. The addition of alkylaromatic hydrocarbon (R2H) to benzaldehyde (R1H) retards the rate of the initiated oxidation [36-39]. The rate of co-oxidation obeys the equation [37] ... 

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],... 

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