Nuclear magnetic resonance study of exchanging systems—IV : Complete line shape analysis of nitrogen inversion of ethylenimine by the density matrix method

Abstract

An NMR spectrum of completely dehydrated ethylenimine 1 in liquid phase was found to show well resolved multiplets for the aziridine ring protons at room temperature. The computer analysis was made to determine the NMR parameters. Temperature dependent NMR spectra show that the nitrogen inversion of 1 is slow enough in the NMR time scale at room temperature. In order to obtain the kinetic parameters of this inversion, the complete line shape analysis for the NMR spectra of 1 as an AA′BB′C spin system was performed using the density matrix method, and fitting the calculated spectra with the observed at various temperatures. The activation parameters are obtained as follows: Ea = 15·9±0·4 Kcal/mole Δ ≠ = 17·1±0·8 Kcal/mole ΔH ≠ = 15·3±0·4 Kcal/mole at 25·° ΔS ≠ = −6·2+-1·2 e.u. Some discussion is made about the activation parameters of the nitrogen inversion of various aziridines.