Surprisingly Small Effect of an a-CF₃ for a-CH₃ Substitution on l-(4-Methoxyphenyl)ethyl Cation Reactivity¹

Experimental studies on the effect of the strongly electron withdrawing a-CF₃ group on carbocation stability have been restricted to documenting the large rate-retarding effect on the rate constants for solvolysis by rate-determining carbocation formation.^{2, 3}Little is known about the effect on the reverse reaction of carbocation with nucleophiles; however, chemical intuition suggests that a highly destabilized a-CF₃-substituted cation will be more reactive than the a-CH₃ counterpart. I wish to report that, contrary to intuition, an a-CF₃ for a-CH₃substitution at 1 has little effect on the rate constant for the reaction of the l-(4-methoxyphenyl)ethyl cation with aqueous trifluoroethanol.