Résonance magnétique nucléaire du noyau 14N par Transformée de Fourier

¹⁴N-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 ¹⁴N-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 ¹⁴N-nuclei contained in the same sample. Different experiments have to be performed, optimizing the spectrometer parameters for each ¹⁴N-resonance of appreciably different linewidth. The technique is applied to three different problems. ¹⁴N-relaxation in symmetrical ammonium salts is shown to arise from reorientation of the water dipoles. The use of a double spin-probe, ¹³C-¹⁴N, 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.