Other NMR Studies

The previously discussed conformational study of 3-substituted thietane oxides using lanthanide shift reagents185 corroborates the conclusions derived from other NMR studies and suggests that all rrans-3-substituted thietane oxides prefer an equatorial oxygen conformation when the thietane oxides are bound to shift reagents. 

In still other NMR studies of mixtures, Douglass and McBrierty have considered the homogeneity of polyvinylidene fluoride - poly methylmethacrylate blends.(38) Here the energy exchange between proton and fluorine magnetic spins is efficient only if the nuclei are adjacent. The results indicate, when taken around 40°C, that either the fluorine nuclei in a 40 polyvinylidene fluoride/60 poly methylmethacrylate blend are... 

Other NMR studies of H bonding systems at various concentrations have been made but have been interpreted in less detail. Cohen and Reid found the limiting shift at zero concentration, So, of H2O, CHaOH,... 

Ab initio calculations have been made of H, O, A1 and Si NMR parameters for sodium aluminosilicate glasses and hydrous silica.331 Two-dimensional 170 3Q MAS-NMR experiments on sodium aluminosilicate glass gave evidence for A1 O Al links.332 27A1 NMR spectra were used to study structural localisation of Al3+ in aluminosilicate clays.333 170 MAS-NMR and MQ MAS-NMR experiments have been carried out on hybrid aluminosilicate xerogels, providing evidence for Si-O-Al and Si O Si sites.334 Several other NMR studies have been made on aluminosilicate glasses and related systems.335 338... 

For many years, relaxation studies in nuclear magnetic resonance were mostly performed by physicists. Even now a survey of the NMR literature shows that among chemists relaxation studies remain less popular than chemical shift or coupling constant studies. We shall not argue about the relative interest of relaxation studies compared with other NMR studies, but we can certainly claim that relaxation time measurements lead to information of great importance for chemists as well as for physicists (and even for biologists and more recently for physicians). 

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