Nucleophilic Substitution Reaction of Phenylmethanesulfonyl Halides with Anilines

Article abstract of DOI:10.1021/ja00258a036

Kinetic studies on the nucleophilic substitution reaction of Y-substituted phenylmethanesulfonyl halides with X-substituted anilines in methanol-acetonitrile have been carried out in order to elucidate the reaction mechanism.The phenylmethanesulfonyl fluorides (PSF) had markedly lower rates and smaller magnitudes of ρ_X and ρ_Y values compared with those for the chlorides (PSC).On the contrary, however, the magnitude of the cross-interaction constant <*>ρ_XY<*> was greater for PSF than for PSC, so that the degree of bond making in the transition state is actually greater in the reaction of PSF as compared with that for PSC.We have thus demonstrated that extensive charge transfer from a nucleophile to a substrate does not necessarily mean a tight bond in the transition state.Moreover the nonzero ρ_XY values obtained for both PSC and PSF are taken as evidence in support of a common, associative S_N2 mechanism for the two halides.