Solvolyses of tosylates IIB and IIC in a variety of solvents were found to give excellent linear log k - Y(BnOTs) plots (R = 0.997 and SD = 0.022) and negative DELTAS(not-equal) for IIB, but slight deviations (R = 0.987 and SD = 0.047) from lineation and positive DELTAS(not-equal) for several cases for IIC. Limiting S(N)1 mechanisms with steric hindrance to resonance and solvent intervention at the cationic transition state could thus be confirmed. The inconsistency between theoretical and observed trend of DELTAH(not-equal) is attributed to the neglect of solvent effect in MO calculations. Deductions linking theoretical calculation and solvolytic experiments should be drawn with caution.
