Techniques for studying high resolution nuclear magnetic resonance spectra have been considerably broadened in recent years. The most far reaching development—pulse Fourier transform (FT) methods—is discussed in detail. Applications of FT techniques to measurement of relaxation times and to enhancement of weak signals, especially from natural abundance 13C, are reviewed. Double resonance methods, particularly the nuclear Overhauser effect, and the use of lanthanide shift reagents are also covered in this “mini-review.”
T2 can be appreciably less than T1 if chemical exchange occurs or if the nucleus in question is spin-coupled to a more rapidly relaxing nucleus. Processes other than the magnetic dipole interaction discussed here can also influence T1. For a more detailed, but introductory level, treatment of relaxation, see, for example, Farrar and Becker,9 Chap. 4.
9.
FarrarT. C.BeckerE. D., Pulse and Fourier Transform NMR (Academic Press, New York, 1971).
AllerhandA.GutowskyH. S., J. Chem. Phys.41, 2115 (1964).
16.
FreemanR.WittekoekS., J. Mag. Resonance1, 238 (1969).
17.
For a more extensive treatment of Fourier transform NMR spectroscopy, see the following paper by D. A. Netzel.
18.
For a discussion of Fourier transform spectroscopy in the optical region, see HorlichG., Appl. Spectrosc.22, 17 (1968).
19.
ErnstR. R.AndersonW. A., Rev. Sci. Instr.37, 93 (1966).
20.
For further details on the instrumental and computer requirements for Fourier transform NMR, see Reference 9, Chap. 5.
21.
ErnstR. R., J. Mag. Resonance3, 10 (1970); KaiserR., J. Mag. Resonance3, 28 (1970).
22.
VoidR. L.WaughJ. S.KleinM. P.PhelpsD. E., J. Chem. Phys.48, 3831 (1968).
23.
FreemanR.HillH. D. W., J. Chem. Phys.54, 301 (1971).
24.
For further details and references, see HoffmanR. A.ForsénS., Progr. NMR Spectrosc. 1, 15 (1966).
25.
See, for example, McFarlaneW., Chem. Brit.5, 142 (1969).
26.
KuhlmannK. F.GrantD. M.HarrisR. K., J. Chem. Phys.52, 3439 (1970).
27.
If paramagnetic species, including dissolved atmospheric oxygen, are present, interactions with the large magnetic moment of the electron serve as an efficient relaxation mechanism, and NOE data are of little value.
28.
IsonoK.AsahiK.SuzukiS., J. Am. Chem. Soc.91, 7490 (1969).
29.
J. H. Y. SchirmerR. E., The Nuclear Overhauser Effect (Academic Press, New York, 1971).
30.
See, for example, KowalewskiV. J., Progr. NMR Spectrosc. 5, 1, (1969).
31.
For details, see StothersJ. B., Carbon-13 NMR (Academic Press, New York, 1972); LevyG. C.NelsonG. L., 13C NMR for Organic Chemists (Wiley-Interscience, New York, 1972).
32.
AllerhandA.DoddrellD.KomoroskiR., J. Chem. Phys.55, 189 (1971).
33.
For a review of 15N studies, see LichterR. L., Determination of Organic Structures by Physical Methods (Academic Press, New York, 1971), Vol. 4; RandallE. W.GilliesD. G., Progr. NMR Spectrosc. 6, 119 (1971).
34.
BriggsJ. M.FarnellL. F.RandallE. W., Chem. Commun. p. 680 (1971).
35.
For a discussion of these multiple pulse methods, see Reference 9, pp. 80–82.
36.
HinckleyC. C., J. Am. Chem. Soc.91, 5160 (1969).
37.
RondeauR. E.SieversR. E., J. Am. Chem. Soc.93, 1522 (1971).
38.
DemarcoP. V.ElzeyT. K.LewisR. B.WenkertE., J. Am. Chem. Soc.92, 5734 (1970).
39.
See, for example, ShapiroB. L.HlubucekJ. R.SullivanG. R.JohnsonL. F., J. Am. Chem. Soc.93, 3281 (1971).
40.
See, for example, GansowO. A.WillcottM. R.LenkinskiR. E., J. Am. Chem. Soc.93, 4295 (1971).
