Approaches to Mechanisms of Skeletal Rearrangements

In the case of small molecules, bond shift is the only possible isomerization 

The use of labeled molecules also allows a determination of the contribution of self-isomerization, that is, of molecules formed by isomerization but having the same structure as the reactant. The formation of such molecules 

During the past two decades, the isomerization of pentanes and hexanes has very often been used as a test reaction in the study of particle size or alloying effects. In these studies, the product distribution, and especially the percentage of cyclic molecules (cyclopentane or methylcyclopentane), have often been used for estimating the contribution of the cyclic mechanism. 

Assuming further a steady-state concentration C for the cyclic intermediate and a pseudounimolecular reaction (42), the mole fractions of reactant and product may be expressed as Eq. (1)  

Since the adsorption rate constant of the cyclic product k, is always much larger (by two to three orders of magnitude) than the dehydrocyclization rate constants 2 and /C3, even at very small conversions where (1 — ) 

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