Nucleophilic substitution reactions of allyl arenesulphonates with anilines and N,N-dimethylanilines

Abstract

Kinetic studies of the reactions of allyl arenesulphonates, I, with anilines and N,N-dimethylanilines in acetonitrile at 45.0 °C are reported. The sign and magnitude of the cross-interaction constants ρ_xz(andβ_xz) between substituents in the nucleophile (X) and leaving group (Z) indicate that the transition state (TS) for I is relatively tight and is similar to that for the corresponding reactions of ethyl systems, rather than for benzyl systems. Variations of the simple Hammett (and Brønsted) coefficients ρ_x(β_x) and ρ_x(β_x) with substituents Z and X, respectively, are consistent with the trend expected from a positive ρ_xzi.e., that predicted by the potential energy surface diagram. The kinetic isotope effects involving N-deuteriated anilines support the mechanism proposed based onρ_xz(β_xz) for the reactions of I, i.e., an associative S_N2 process with an earlier TS for a stronger nucleophile and/or a better leaving group.