Gas Phase NMR
Chapter 5: 17O and 33S NMR Spectroscopy of Small Molecules in the Gas Phase
Published:09 Feb 2016
17O and 33S NMR are demanding methods in experimental work, especially when the measurements are performed for gaseous samples. Nevertheless the oxygen and sulfur measurements in the gas phase are presently possible due to significant improvements in technical instrumentations e.g. higher fields generated in superconducting magnets, better sensitivity of NMR probes and development of various pulse sequences. The main achievements in gas phase 17O and 33S NMR research into simple organic and inorganic compounds are reviewed and recent experimental and theoretical works involving the nuclear magnetic shielding, indirect spin–spin coupling constants and other parameters, which can be deduced from simple 17O and 33S spectra, are examined. The important results of shielding calculations are mentioned. Recently the calculations were jointly used with the gas phase experiments for the determination of new values for the 17O and 33S nuclear magnetic dipole moments. As shown the most difficult challenges for theoretical methods are spin–spin coupling predictions. Several examples of such calculations along with experimental results are given in this chapter. In a few cases, we also present the experimental results for liquids, which can reflect the presence of intermolecular interactions in oxygen and sulfur NMR spectra.