Part I. The Configurational Stability of Primary Grignard Reagents. Part II. Applications of Nuclear Magnetic Resonance Spectroscopy to the Study of Molecular Asymmetry

Abstract

Part I The Configurational Stability of Primary Grignard Reagents Examination of the temperature dependence of the nuclear magnetic resonance spectrum of 3,3-dimethylbutylmagnesium chloride in diethyl ether solution indicates that inversion of configuration at the methylene group of this Grignard reagent occurs with an approximate rate of 10 sec.⁻¹ at room temperature. The dependence of the rate of inversion on solvent and on the structure of the Grignard reagent is discussed in terms of possible mechanisms for the inversion. Part II Applications of Nuclear Magnetic Resonance Spectroscopy to the Study of Molecular Asymmetry The methylene protons of 1-phenylethyl benzyl ether are magnetically non-equivalent and display an AB-type nuclear magnetic resonance spectrum. The variation in the spectrum of this compound and in the spectra of other structurally similar ethers with solvent indicates that the principal contribution to the magnetic non-equivalence of the methylene protons originates in the magnetic anisotropy of the phenyl group bonded directly to the methylene group. It is suggested that the solvent dependence of these spectra reflects changes in the populations of the possible rotational conformations open to the molecule.