The rates for the reaction of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines under pressure in acetonitrile at 60°C were measured by an electrical conductivity method. From the values of r X , r Y and r Z , it was concluded that bond formation between the nucleophile and reaction center is more advanced in the transition state (TS). The magnitude of the correlation interaction term, r ij , was used to determine the structure of the transition state for the S N reaction. As the pressure increases, the Hammett reaction constants r X and r Y decrease, but the correlation interaction coefficients, r XZ and r YZ , increase. The results indicate that the reaction of (Z)-phenylethyl (X)-benzenesulfonates with (Y)-pyridines probably proceeds via a dissociative S N 2 reaction and with increasing pressure the TS moves to an early position. This result agrees with the MOFJ diagram interpretation and shows that the correlation interaction term, r ij , can be a useful tool for determining the structure of the TS.