Methylcyclopentane ionization

A—The ion was trapped by solvolysing in the presence of methylcyclopentane. B—Methylcyclopentane was added 10 minutes after ionization. 

Both methylcyclopentane and cyclohexane were found to give the methylcyclo-pentyl ion, which is stable at low temperature, in excess superacid.22 When alkanes with seven or more carbon atoms were used, cleavage was observed with formation of the stable ferf-butyl cation 4. Even paraffin wax (see Section 2.2.2.2 on Magic Acid) and polyethylene ultimately gave the ferf-butyl cation 4 after complex fragmentation and ionization processes. 

Protolytic ionization of methylcyclopentane gives an equilibrium mixture of the tertiary 1-methyl-1-cyclopentyl cation (29) (more stable by about 40 kJ/mol) and the secondary cyclohe l cation (32) (Scheme 5). At low temperature, irreversible reaction of 29 with CO leads to ion 30, which, after reaction writh ethanol, gives the 31 ester. Product composition, in this case, reflects the difference in stability of the intermediate carbocations. Since the carbonylation step is reversible at higher temperature, and carbocation 32 has a much higher affinity for CO, the concentration of 33 in solution continuously increases to yield, after quenching with ethanol, the 34 ester. This is an example of a kinetically controlled product formation through a thermodynamically unfavorable intermediate. 

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