The sum of the rate constants for solvolysis and scrambling of carbon bridging and nonbridging oxygen-18 at 4-MeC 6 H 4 CH(CF 3 )OS( 18 O 2 )Tos in 50/50 (v/v) trifluoroethanol/water, (k solv + k iso ) = 5.4 × 10 −6 s −1 , is 50% larger than k solv = 3.6 × 10 −6 for the simple solvolysis reaction of the sulfonate ester. This shows that the ion pair intermediate of solvolysis undergoes significant internal return to form reactant. These data give a value of k −1 = 1.7 × 10 10 s −1 for internal return of the carbocationanion pair to the substrate. This rate constant is larger than the value of k −1 = 7 × 10 9 s −1 reported for internal return of an ion pair between the 1-(4-methylphenyl)ethyl carbocation and pentafluorobenzoate anion to the neutral ester (4-MeC 6 H 4 CH(CH 3 )O 2 CC 6 F 5 ) in the same solvent. The partitioning of ion pairs to the 1-(4-methylphenyl)ethyl carbocation and to the highly destabilized 1-(4-methylphenyl)2,2,2-trifluoroethyl carbocation is compared and contrasted.