Nucleophilic substitution reaction of cumyl arenesulfonates with anilines

Abstract

The nucleophilic substitution reaction of cumyl arenesulfonate with aniline has been investigated. The reaction in acetonitrile proceeds by the S_N2 mechanism with probable frontside nucleophilic attack. The large magnitude of ρ_xz(=–0.75) obtained results in an observable sign reversal of ρ_z at _x= 0.83, with a negative ρ_z value for σ_x > _x. This rather unusual phenomenon can be rationalized by a strong interaction between the nucleophile and leaving group due to their close proximity in the transition state, which in turn is a result of the frontside nucleophilic attack. The reactions in methanol indicate that the S_N1 channel competes with the S_N2 pathway and ion-pair return is observed when the aniline nucleophile concentration is low.