Nucleophilic reactivity of methoxide ion at C-5 of 4-nitro-7-X-benzofurazans: a kinetic and thermodynamic investigation of Meisenheimer complexes

Abstract

A kinetic and thermodynamic investigation of the Meisenheimer complexes formed at C-5 of 4-nitro-7-X-benzofurazans has been carried out. The results indicate some influence of resonance stabilization in the ground state due to cross-conjugation between X and the nitro- and (aza-) groups, the observed maximum rate lowering factor being ca. 5 for X = OMe. However the importance of repulsive interactions in the transition state between the linked group and the nucleophile is recognized. The conclusions are compared with some suggestions previously made for analogous complexes in trinitrobenzene.