Carbocation lifetimes that are independent of carbocation stability: the reaction of α-substituted 4-methoxybenzyl carbocations

The α-methoxy-4-methoxybenzyl carbocation reacts with the solvent trifluoroethanol–water (50 : 50 v/v) with a rate constant ks= 3 × 107 s–1; ks increases by less than twofold when the carbocation is destabilised by replacement of the strongly electron donating α-OMe substituent by the strongly electron withdrawing α-CF3 substituent.