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NMR, basic principles and progress, vol. 22. Isotope effects in nmr spectroscopy
446
BOOK
REVIEW!;
of structural formulas of complex molecules, and an alphabetical list of compound names is provided. It is gratifying to note the clear distinction which is made between the directions of the shielding scale and of the chemical-shift scale. The relative extent of researchactivities in solid-state NMR is well illustrated by the numbers of pagesdevoted to the various sections in the book: hydrogen, 12; carbon, 46; nitrogen, 10; fluorine, 12; silicon, 9; phosphorus, 3 1; and 16 miscellaneouselements, 24. This is a valuable reference volume, provided at modest cost, and it should be in the hands of anyone working in solid-state NMR. W.S.B. NMR, Basic Principles and Progress, Vol. 22. Isotope Effects in NMR Spectroscopy,
edited by P. Diehl, E. Fluck, H. Gunther, R. Kosfeld, and J. Seelig. Springer-Verlag, New York/Berlin, 1990. 173 pages. $75.00. ISBN: O-387-51286-1. There are three sections in this book. The first, by S. Berger, discusses models for the effects of deuterium on carbon- 13 and fluorine- 19 spectra. The theme is that most of the effects can be understood as being quite analogous to the usual substituent effects on shifts, or on reactivity as correlated by physical organic chemists. Thus the isotope effects are considered to be a result of perturbation of the electronic cloud, related to delocalization of electrons in aromatic systems or to phenomena such as “hyperconjugation.” Attention is also called to a difference between what may be described as “intrinsic” isotope effects and what are called, in a somewhat confusing terminology, “equilibrium” effects, meaning that they are indirectly produced because the isotopic substitution has produced a shift in a conformational equilibrium. The second chapter, by N. M. Sergeyev,deals with the experimental evidence for isotope effects on the magnitudes of spin-spin coupling constants. Because these changes are extremely small, they are very difficult to measure, and the various sources of experimental error are analyzed in detail. One must distinguish, of course, between changes produced by the isotope in coupling constants in which the substituted atom is directly involved and those produced in couplings involving two other atoms. Since the magnetogyric ratio of a coupled atom is involved in the value of J, isotope influences of the first or direct sort, while expected to be the largest, can be suitably interpreted only if precise values of the ratio of the two y’s are available. A critical evaluation of results reported in the literature is given, but there is no attempt to develop a theory based on these results. A three-page appendix lists some additional and recent reports. The final chapter, by J. M. Risley and R. L. Van Etten, constitutes more than half the book. Oxygen- 18 isotope shifts in carbon- 13 and nitrogen- 15 spectra are reviewed. Following a brief introduction, extensive tables of data and some discussion of generalizations drawn from the data are presented. Examples of organic, inorganic, and biosynthetic reaction mechanism studies based on the use of this isotope are listed and described. Finally, references are given to reviews of the theory of oxygen-l 8 isotope effects and to attempts to predict their values on the basis of these theories. W.S.B.
BOOK
REVIEW!;
of structural formulas of complex molecules, and an alphabetical list of compound names is provided. It is gratifying to note the clear distinction which is made between the directions of the shielding scale and of the chemical-shift scale. The relative extent of researchactivities in solid-state NMR is well illustrated by the numbers of pagesdevoted to the various sections in the book: hydrogen, 12; carbon, 46; nitrogen, 10; fluorine, 12; silicon, 9; phosphorus, 3 1; and 16 miscellaneouselements, 24. This is a valuable reference volume, provided at modest cost, and it should be in the hands of anyone working in solid-state NMR. W.S.B. NMR, Basic Principles and Progress, Vol. 22. Isotope Effects in NMR Spectroscopy,
edited by P. Diehl, E. Fluck, H. Gunther, R. Kosfeld, and J. Seelig. Springer-Verlag, New York/Berlin, 1990. 173 pages. $75.00. ISBN: O-387-51286-1. There are three sections in this book. The first, by S. Berger, discusses models for the effects of deuterium on carbon- 13 and fluorine- 19 spectra. The theme is that most of the effects can be understood as being quite analogous to the usual substituent effects on shifts, or on reactivity as correlated by physical organic chemists. Thus the isotope effects are considered to be a result of perturbation of the electronic cloud, related to delocalization of electrons in aromatic systems or to phenomena such as “hyperconjugation.” Attention is also called to a difference between what may be described as “intrinsic” isotope effects and what are called, in a somewhat confusing terminology, “equilibrium” effects, meaning that they are indirectly produced because the isotopic substitution has produced a shift in a conformational equilibrium. The second chapter, by N. M. Sergeyev,deals with the experimental evidence for isotope effects on the magnitudes of spin-spin coupling constants. Because these changes are extremely small, they are very difficult to measure, and the various sources of experimental error are analyzed in detail. One must distinguish, of course, between changes produced by the isotope in coupling constants in which the substituted atom is directly involved and those produced in couplings involving two other atoms. Since the magnetogyric ratio of a coupled atom is involved in the value of J, isotope influences of the first or direct sort, while expected to be the largest, can be suitably interpreted only if precise values of the ratio of the two y’s are available. A critical evaluation of results reported in the literature is given, but there is no attempt to develop a theory based on these results. A three-page appendix lists some additional and recent reports. The final chapter, by J. M. Risley and R. L. Van Etten, constitutes more than half the book. Oxygen- 18 isotope shifts in carbon- 13 and nitrogen- 15 spectra are reviewed. Following a brief introduction, extensive tables of data and some discussion of generalizations drawn from the data are presented. Examples of organic, inorganic, and biosynthetic reaction mechanism studies based on the use of this isotope are listed and described. Finally, references are given to reviews of the theory of oxygen-l 8 isotope effects and to attempts to predict their values on the basis of these theories. W.S.B.