Nuclear magnetic resonance spectroscopy shift reagents

Nuclear Magnetic Resonance Spectroscopy.—As noted above, conformational analysis of bicyclo[3.3.1]nonanes is still a topic of considerable interest. A variable-temperature n.m.r. analysis now provides the first case in which the boat-chair-chair-boat equilibrium is directly observed in the amines (17) and (18). In a related case, re-examination of the acetal (19) suggests that the preferred conformation involves a chair carbocyclic ring and a boat heterocyclic ring. This conclusion was made by n.m.r. analysis, using lanthanide shift reagents, by a study of nuclear Overhauser effects, and by measurement of relaxation times of protons. Details have been reported for other 3-azabicyclo[3.3.1]nonanes, and the non-additivity of substituent effects on chemical shifts in 9-thiabicyclo[3.3.1]non-2-enes has been analysed. Both and n.m.r. data have been reported for a series of 9-borabicyclo[3.3.1]non-anes and their pyridine complexes. 

In Experiment 28B (optional), you may use nuclear magnetic resonance spectroscopy to determine the relative amounts of (R) and (S) enantiomers produced in the chiral reduction of ethyl acetoacetate. This part of the experiment requires the use of a chiral shift reagent. 

Glockhart 1976 Lanthanide shift reagents in nuclear magnetic resonance spectroscopy. CRC Critical Reviews in Anal Chem 6 69-130... 

Elgavish GA (1993) Shift reagent-aided 23]sja nuclear magnetic resonance spectroscopy. In Pohost GM (ed) Cardiovascular Applications of Magnetic Resonance, pp 371-391. Mount Kisco, NY Futura. 

Cockerill AF, Davies GLO, Harden RC and Rackham DM (1973) Lanthanide shift reagents for nuclear magnetic resonance spectroscopy. Chemical Reviews 73 553-588. 

Naritomi H., M. Kanashiro, M. Sasaki, Y. Kuribayashi, T. Sawada, In vivo measurements of intra-and extracellular Na" " and water in the brain and muscle by nuclear magnetic resonance spectroscopy with shift reagent. Biophys. J. 52, 611—616 (1987). 

J. Reuben, in Progress in Nuclear Magnetic Resonance Speetroscopy , Vol. 9, Pt. 1 Lanthanide Shift Reagents m NMR Spectroscopy Principles, Methodology and Applications , Pergamon Press, Oxford, 1973. 

Since the 1950s, nuclear magnetic resonance (NMR) has found wide application in the solution of chemical problems, including numerous applications in the field of Grignard reagents. Chemical shift and spin-spin-coupling data enable the chemist to determine the location of magnetically active nuclei in a molecule of interest, and to obtain preliminary structural information often not readily deducible by other methods of spectroscopy. 

Low resolution mass spectrometry (MS), especially in tandem with gas chromatography, and nuclear magnetic resonance (NMR) spectroscopy have been reviewed with respect to their application to pesticide residue analysis. Sample preparation, direct probe MS analysis, GC-MS interface problems, spectrometer sensitivity, and some recent advances in MS have been studied. MS analyses of pesticide residues in environmental samples (malathion, dieldrin, dia-zinon, phenyl mercuric chloride, DBF, and polychlorinated biphenyls) have been illustrated. Fragmentation patterns, molecular ions, isotope peaks, and spectral matching were important in the identification of these pesticides. The sensitivity limitations of NMR and recent improvements in sensitivity are discussed along with examples of pesticide analyses by NMR and the application of NMR shift reagents to pesticide structure determinations. 

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