Correlation of the rates of solvolysis of arylmethyl p-toluenesulfonates: application of the aromatic ring parameter and a discussion of similarity models

The specific rates of solvolysis of benzyl p-toluenesulfonate and nine benzylic-ring-substituted derivatives are satisfactorily correlated using N-T and Y-OTs scales within the extended Grunwald-Winstein equation. Addition of a third term, governed by the aromatic ring parameter, shows the additional term to be statistically significant. As one incorporates increasingly more electron-withdrawing substituents, the sensitivities towards changes in solvent nucleophilicity (l) increase, and those towards changes in ionizing power and changes in the aromatic ring parameter decrease. The trend of l values can be very nicely shown, with very precise correlations, using an internally generated scale of Y values. However, it is demonstrated that there is no overall advantage to use of an internally generated scale if one ultimately wishes to make a comparison with sensitivity values generated using an external scale of Y values.