Cyclopentane skeletal structure

Skeletal rearrangement reactions over Pt single crystals have been studied for methyl cyclopentane, 2- and 3-methylpentane350 and for n-hexane.3sl One conclusion351 is that whereas aromatization reactions are very sensitive to surface structure [Pt(l 11)> Pt(100)], isomerization, Cs-cyclization, and hydrogenolysis reactions display little dependence on structure. Temperature and H2 pressure are more important in affecting the selectivity. 

Contrary to previous exercises, none of the structural characteristics of the starting material can be identified in the product, save perhaps for the gem-dimethyl unit. Also, while I includes 9 skeletal carbons (this word is used to exclude those carbon atoms in the substituents in order to simplify the analysis of structural changes), target compound II contains 10. Obviously, this requires the incorporation of one functional carbon from the peripheral substituents, conceivably one of the nitriles, to the molecular backbone. This in turn implies that the five-membered ring of II is not the same cyclopentane unit of I. 

C=C—C—C—C—C. Isomerization to a methylpentane would result in localizing the carbonium ion on the tertiary position. This structure can no longer ring close to a cyclopentane but only to a highly strained cyclobutane. Since skeletal isomerization occurs readily at reforming conditions, most of the n-hexane would be converted to isohexane or cracked products rather than to cyclopentane. 

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