Exchange of alkanes with

Figure 4. Transition state for H/H exchange of alkanes with zeolites.

It will not have escaped notice that adsorbed species implicated in the exchange of alkanes with deuterium are formally the same as those invoked in the hydrogenation of alkenes indeed the reiteration of the alkyl-alkene transformation (process 6.J) held responsible for multiple exchange in linear and branched alkanes, and designated the afi exchange mechanism, is on the face it of identical with the old and well-tried Horiuti-Polanyi mechanism for alkene hydrogenation. This will be discussed further in the next chapter (sections 7.1 and 7.21), but briefly it supposes the sequential addition of two hydrogen atoms to some adsorbed form of the alkene, e.g. 

An interesting type of reactions including the activation of chemically inert C—bonds is based on oxidative addition. This process appears, in particular, in isotope exchange of alkanes with molecular hydrogen. 

Efficient oxidation of alkanes with molecular oxygen can be attained using N-hydroxyphthalimide combined with Co(acac) (n = 2,3).1121 According to a new concept, photocatalyzed selective oxidation of small hydrocarbons at room temperature is carried out over alkali or alkaline-earth ion-exchanged zeolites.1122... 

Ligand exchange of BAIB with magnesium perchlorate in CH2Cl2-MeCN, followed by the introduction of terminal and cyclic alkenes, has been reported to give WdnaZ-bis(perchlorato)alkanes [45]. The cyclic alkenes gave cis-adducts under these conditions. 

To the best of our knowledge, there are no published data on the reactions of alkanes with H2 over palladium single crystals. Deuterium exchange reactions with various alkanes over palladium films were extensively investigated by Kemball et al. (39-42). Because those results were already discussed in several excellent review articles (43-46), we do not intend to dwell upon analyzing all the data at greater length. We only specify here the basic characteristics of Pd films exhibited in D2/alkane reactions ... 

In view of the proven multistep catalytic process, transport of the reacting species from one type of site to another before desorption as an alkane, cycloalkane, or benzene seems necessary. Since desorbed olefin plays a significant role in exchange of cycloalkanes with deuterium on Pd films even at ambient temperatures, olefins and even dienes could be responsible in the transport steps. It is useful to recall that this is, in fact, the basis of the classic theory of dualfunctional catalysis. 

Tateiwa, J. I., H. Horiuchi, and S. Vemura. 1994c. Mn2+-exchanged clay-catalysed oxidation of alkanes with tert-butyl hydroperoxide. Chem. Commun. 2567-2568. 

Applications of cation-exchanged ZSM-5 include ammoximation of alkanes with Co ZSM-5, water-tolerant oxidation of NH3 to N2 with Pd-ZSM-5, low-temperature catalytic combustion of CH4 with Pd-ZSM-5, wet N2O decomposition with Co-ZSM-5, NOv reduction with CH4 even in the presence of excess O2 with Co ZSM-5 and catalytic decomposition of NO in the absence of O2 with Cu ZSM-5. In most of these cases, the activity (rate, conversion and/or selectivity) of the redox ZSM catalysts is much higher than when the corresponding metal is supported on traditional oxides [125]. 

It may also be noted the aqueous acid solutions of K2PtCl4 also homogeneously catalyze H-D exchange in alkanes with relative rates opposite to the ones above, namely primary CH > secondary CH > tertiary CH.27 The mechanism of exchange is not clear but it may involve an oxidative addition of C—H to Ptu (Chapter 24). 

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