Résonance magnétique nucléaire du noyau ¹⁴N par Transformée de Fourier

Abstract 14 N‐NMR. measurements using the Fourier Transform technique are presented and compared to C. W. experiments. The F. T. technique is especially advantageous for relaxation time measurements. However, since 14 N‐nuclei may have widely different relaxation times, it is often not possible to have optimal gain in sensitivity (as compared to C. W. measurements) in a single F. T. experiment for different 14 N‐nuclei contained in the same sample. Different experiments have to be performed, optimizing the spectrometer parameters for each 14 N‐resonance of appreciably different linewidth. The technique is applied to three different problems. 14 N‐relaxation in symmetrical ammonium salts is shown to arise from reorientation of the water dipoles. The use of a double spin ‐ probe , 13 C‐ 14 N, allows the determination of the electric field gradients in cyclic ammonium salts. The electronic distribution is especially distorted from tetrahedral symmetry in the highly strained N, N‐dimethyl‐aziridinium cation. Finally, electric and dynamic effects in ion pairing may be studied as shown on the case of tetrabutylammonium iodide in water and in benzene.