Croos-Interaction Constants as a Measure of the Transition-State Structure. 14. Nucleophilic Substitution Reactions of 1-Phenyl-2-propyl Benzenesulfonates with Anilines in Methanol

Article abstract of DOI:10.1021/jo00015a022

The kinetics of the reactions between 1-phenyl-2-propyl benzenesulfonates (PPB) and anilines in methanol at 65.0 deg C are investigated, and the mechanism is discussed on the basis of various selectivity parameters, especially on the cross-interaction constants, ρ_ij.The aryl participation is significant only with the p-CH3O-substituted substrate. ρ_XZ is positive, and accordingly the transition state (TS) variations with subbstituents are consistent with those predicted by the potential energy surface diagram.The TS is of an intermediate type between that for an associated (tight) and a dissociated (loose) S_N2 process; it is rather tight, but bond breaking is ahead of bond making with positive charge development at the reaction center in the TS.The possibility of front-side attack witha four-center TS is precluded because of strong steric hinderance in a close approach of the two bulky groups, the nucleophile and leaving group, on the same side in the front-side attack.