Application of correlation interaction coefficients. Part 1. Structure-reactivity relationship of phenylethyl arenesulfonates under high pressure

The rates for the reaction of (Z)-phenylethyl (X)-benzenesulfonates with (Y )-pyridines under pressure in acetonitrile at 60 degrees C were measured by an electrical conductivity method. From the values of rho(X), rho(Y) and r ho(Z), it was concluded that bond formation between the nucleophile and rea ction center is more advanced in the transition state (TS). The magnitude o f the correlation interaction term, rho(ij), was used to determine the stru cture of the transition state for the SN reaction. As the pressure increase s, the Hammett reaction constants rho(X) and rho(Y) decrease, but the corre lation interaction coefficients, rho(XZ) and rho(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 i ncreasing pressure the TS moves to an early position. This result agrees wi th the MOFJ diagram interpretation and shows that the correlation interacti on term, rho(ij), can be a useful tool for determining the structure of the TS. Copyright (C) 1999 John Wiley & Sons, Ltd.