Reactions of Cyclic Alkanes with Hydrogen

Although the C—C—C bond angles in the C5 ring are close to that for tetrahedral carbon, the fission of a C—C bond by hydrogenolysis occurs more readily than that of linear alkanes. Reaction takes place at lower temperatures and with lower activation energies, and the order of reaction in hydrogen (for methylcyclopentane) is positive, where for an acyclic alkane it would be negative. This is 

TABLE 14.4. Hydrogenolysis of Methylcyclopentane on Platinum Catalysts Selectivity Parameters 

Column headings D = fractional dispersion, d = size (nm) S subscripts 6 2-methylpentane 3 = 3-methylpentane n = n-hexane S = mechanistic selectivity (%). EUROPT-l (6% Pt/SiOj)  

There appears to be some disagreement as to whether ring-enlargement of MCP to cyclohexane and thence rapidly to benzene can occur on catalysts having only a metallic function. It does not take place on single-crystal 

Methylcyclopentane reacted with hydrogen on Rh/Si02 and Rh/Al203 at 500 K to give quantities of smaller alkanes that fell as the hydrogen pressure was raised 33 3 45-i48 product selectivities ( 60 showed little dependence on this variable or on conversion up to In another study with RI1/AI2O3, 

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