The effect of substituents on the rate of pyramidal inversion of 1-aryl-2,2-dimethylaziridines

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

54 Scopus Citations
View graph of relations

Author(s)

Related Research Unit(s)

Detail(s)

Original languageEnglish
Pages (from-to)4050-4056
Journal / PublicationJournal of the American Chemical Society
Volume92
Issue number13
Publication statusPublished - 1970

Abstract

The influence of electronic effects on the barrier to pyramidal inversion in meta- and para-substituted N-phenyl-2,2-dimethylaziridines has been investigated by an examination of the temperature-dependent nmr spectrum. Rate constants and free energies of activation at the coalescence temperature have been determined. The inversion barrier shows a linear correlation with the Hammett substituent constant σ-(ρ = 2.8-3.3 at -60°). The direction of the substituent effect parallels that previously found for pyramidal inversion at sulfur in sulfoxides and at phosphorus in phosphines, but the magnitude of the effect is greatest in the aziridines. These results are ascribed to conjugation of the lone pair on the inverting center with the attached arene π system, an effect which is more pronounced for first- than for second-row elements, and which finds its maximum expression in the transition state for the inversion process.