2,6-Dimethyl-2-heptyl cation

Doom, 1969 Saunders and Stofko, 1973). The barrier for 1,4-hydride shift in 2,5-dimethyl-2-hexyl cation [12] is some 12-13 kcal mol" (Saunders and Stofko, 1973) which is even higher than for [11]. Going to 1,5-shifts in 2,6-dimethyl-2-heptyl cation [13] either the barrier is drastically decreased to... 

Rationalize the observation that the NMR spectrum of the 2,6-dimethyl-2-heptyl cation at -100°C shows only one peak for the four methyl groups at the ends of the chain. 

Dimethyl- and 2,4,4,6-tetramethyl-heptyl cations The total isotope effect of a CD3-group is independent of conformation (Sunko et al., 1977), and the CDj-substituted cations [155] and [156] can therefore serve as a model for a dihedral angle of 0° whereas the cations [157] and [158] deuteriated in the methylene group provide information on the conformational dependence of the equilibrium isotope effect. 

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