NMR Relaxation Study of Molecules Containing a CO Group. Determination of the 17O Quadrupolar Coupling Constant and of the 13C Shielding Tensor Anisotropy in Solution
✍ Scribed by P. Rubini; D. Champmartin
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 727 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
The NMR relaxation times of the "C(O) nuclei of formanilide, acetanilide, benzamide, benzoic acid, the benzoate anion and glycine were measured for four different magnetic field values, allowing the determination of the contribution of the shielding anisotropy mechanism to the total relaxation rate. The knowledge of the reorientational correlation time of the molecules, determined from measurements of the "C relaxation time of a "C-H fragment, the motion of which is not affected by internal rotations, allowed the calculation of the anisotropy of the "C(O) shielding tensor, Au. From the linewidth of the I7O NMR signals it was also possible to deduce the 1 7 0 quadrupolar coupling constant, 1, of the oxygen nucleus in the CO group. The values of Au and 1 were obtained in solution and were compared with those obtained in the solid state; with the exception of benzoic acid, the Au values for solutions and solids are similar. The relaxation processes were analysed in detail and the ACT and x values are discussed.