15n Nmr Spectroscopy

After the proton and carbon, nitrogen is, with oxygen, the most impor tant atom in organic and especially bioorganic molecules. However, the development of nitrogen spectroscopy is indeed very recent. This is due to the fact that nitrogen-14, which is the naturally abundant iso tope, suffers, for structural studies, from the disadvantages inherent in nuclei with a quadrupolar moment (Table 1.1). Actually, indirect 15N measurements were reported in the early days of double resonance spectroscopy and the first direct detection of 15N resonance signals at the natural abundance level was realized in 1964 (R 17) at 4.33 MHz 1 (~ 1T) using a 15 mm o.d. cell in the field sweep mode (~ 0.16 min- ). Signal-to-noise ratios only of 3-4 were obtained for neat liquids and this low sensitivity of the 15N resonance still remains the main dis advantage for 15 spectroscopy (Table 1.1). However, nitrogen-15 has, N probably more than any other nucleus, benefited from the advances of NMR technology, i.e. Fourier transformation, multinuclear facilities, wide-bore super conducting solenoids, and, with the new generation of spectrometers, 15N-NMR is entering the field of routine investigation. Nevertheless, in spite of these spectacular improvements, obtaining 15N spectra of diluted species or large biochemical molecules is often not very easy and a good knowledge of the relaxation properties pecu liar to 15N may be necessary in order to adjust the pulse sequences and the decoupler duty cycle correctly (Section 2).

To date nitrogen NMR has been discussed in research papers and review articles throughout the scientific literature. It has been our aim in preparing this book to provide a comprehen sive account of the widely spread applications of nitrogen NMR. The relevant literature has been surveyed from the beginnings of NMR until early 1972. The steady annual growth in the number of references cited since 1965 is ample evidence of the ever increasing importance of the subject. Sufficient theoretical and experimental background is given for an understanding of the applications dealt with in later chapters. The basic principles of NMR are developed with a theoretical approach to chemical shifts and spin-spin coupling constants, particular emphasis being given to nitrogen nuclei. Following this the experimental aspects of nitrogen NMR are adequately described. Special emphasis is given to the observable effects of the nuclear quadrupole moment of the 14 N nucleus. It is appro priate that this topic be dealt with in depth since quadrupolar interactions frequently dominate the information available from a study of the 14 N nucleus and other nuclei spin coupled to it. The applications of nitrogen chemical shift data to organic and inorganic molecules are covered in two extensive chapters which include the effects of paramagnetism on nitrogen NMR.

These indexes are valuable volumes in the serial, bringing together what has been published over the past 38 volumes. They include a preface by the editor of the series, an author index, a subject index, a cumulative list of chapter titles, and listings of contents by volume.

Nuclear magnetic resonance (NMR) is an analytical tool used by chemists and physicists to study the structure and dynamics of molecules. In recent years, no other technique has grown to such importance as NMR spectroscopy. It is used in all branches of science where precise structural determination is required and where the nature of interactions and reactions in solution is being studied. Annual Reports on NMR has established itself as a premier means for the specialist and nonspecialist alike to become familiar with new techniques and applications of NMR spectroscopy. * Includes comprehensive review articles on NMR Spectroscopy * NMR is used in all branches of science * No other technique has grown to such importance as NMR Spectroscopy in recent years

This practice-oriented textbook shows how to utilize the huge variety of NMR experiments available today in addition to standard experiments. Intended as a practical guide for students and laboratory personnel, it treats theoretical aspects only to the extent necessary to understand the experiments and to interpret the results. The book is significantly revised and expanded for the 2nd edition, and now includes the nuclei 1H/2H, 13C, 31P, 17O, 15N, 19F, 29Si, 77Se, 113Cd, 117Sn/119Sn, 195Pt, 207Pb and a new chapter on solid state NMR. An expanded set of 50 graded problems offers invaluable help for students, practitioners and laboratory personnel alike.