Cyclopentane methyl-, hydrogenolysis

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. 

Step (c), the reverse of Step (a), may be investigated separately by studying the hydrogenolysis of cyclopentanes and cyclobutanes. In these reactions, the effect of methyl substituents allows one to distinguish between several reaction mechanisms. 

Fig. 15. Turnover frequency TOF versus fraction exposed FE and mean particle size d for the hydrogenolysis of cyclopentane (—) and methyl-cyclopentane (—) on various metal systems (see Table VIII for details of the studies).

The main hydrogenolysis product in Table 11 and Fig. 67 is 1,3-bis(3-methyl-butyl)cyclopentane (peak numbers 6 and 7). It can be obtained separately by adsorption chromatography on silicagel with iso-octane as eluent or by vacuum distillation at 105°C and 13 mm Hg (37). Another procedure is Clemmensen reduction, followed by catalytic hydrogenation, whereby two cis-trans isomers are obtained (37). The 2,4-bis(3-methylbutyl)-2-cyclopentenone (peak number 11) can be obtained by reduction of the dihydrodeoxohumulinic acids or of compound 142 with lithium aluminium hydride and preparative gas chromatographic separation (58). 

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