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Valence-Bond Interpretation of Electron-Coupled Nuclear Spin Interactions; Application to Methane
A valence-bond theory, based on the approximate second-order perturbation method of Ramsey, has been developed for the calculation of the electron-coupled nuclear spin interactions in a 1 molecule. It...
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Interpretation of the Electron-Spin Resonance Spectrum of the Methyl Radical
A valence-bond calculation of the proton hyperfine splitting in the electron-spin resonance spectrum of the methyl radical has been performed. The splitting was computed as a function of the angular c...

Contact Electron-Spin Coupling of Nuclear Magnetic Moments

J. Chem. Phys. 30, 11 (1959); doi:10.1063/1.1729860

Issue Date: January 1959

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Martin Karplus
Noyes Chemical Laboratory, University of Illinois, Urbana, Illinois
The valence-bond theory for the contact electron-spin coupling of nuclear magnetic moments is used to calculate the proton-proton, proton-fluorine, and fluorine-fluorine coupling constants in ethanic and ethylenic molecules. A considerable simplification is introduced into the theory by approximations which reduce the problem to one involving only a small number of electrons and canonical structures. The agreement between calculated and experimental values is such as to demonstrate that the mechanism considered is the one of primary importance for the nuclear coupling in the compounds studied. Of particular interest is the theoretical confirmation of the observation that in ethylenic compounds the trans coupling between nuclei (HH, HF, FF) is considerably larger than cis coupling. ©1959 American Institute of Physics
History: Received September 4, 1958
Permalink: http://link.aip.org/link/?JCPSA6/30/11/1
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ISSN:
0021-9606 (print)   1089-7690 (online)
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REFERENCES (20)
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  1. M. Karplus, Bull. Am. Phys. Soc. Ser. II, 3, 119 (1958).
  2. M. Karplus and D. H. Anderson, J. Chem. Phys. 30, 6 (1959), this issue. This paper is referred to as I hereafter.
  3. For a discussion of the second assumption, see D. M. Grant and M. Karplus (to be published). In that paper it is shown that in most cases an error of less than five percent is introduced by this approximation.
  4. L. Pauling, J. Chem. Phys. 1, 280 (1933).
  5. J. H. Van Vleck, J. Chem. Phys. 1, 219 (1933).
  6. W. G. Penney, Proc. Roy. Soc. (London) A144, 166 (1934);
    7. C. A. Coulson and W. Moffitt, Phil. Mag. 40, 1 (1949).
  7. A procedure for obtaining these integrals empirically is being developed. For acetylene, relatively reliable values for the required linear combinations of the seven s, sigma exchange integrals have been obtained [T. C. Farrar and M. Karplus (to be published)].
  8. H. J. Kopineck, Z. Naturforsch. 5a, 420 (1950).
  9. C. C. J. Roothaan, J. Chem. Phys. 19, 1445 (1951).
  10. R. E. Glick and A. A. Bothner-By, J. Chem. Phys. 25, 362 (1956).
  11. Lemieux, Kullnig, Bernstein, and Schneider, J. Am. Chem. Soc. 80, 2237 (1958);
    12. also, R. V. Lemieux, Karl Folkers Lectures, University of Illinois (May, 1958).
  12. W. S. Galloway and E. F. Barker, J. Chem. Phys. 10, 88 (1942);
    13. but see L. S. Bartell and R. A. Bonham, J. Chem. Phys. 27, 1414 (1957) for another value.
  13. A partial justification of this approximation has been presented by McConnell, J. Mol. Spectroscopy 1, 11 (1957), for aromatic systems.
  14. S. Alexander, J. Chem. Phys. 28, 358 (1958);
    15. Grant, Gutowsky, and Karplus (to be published).
  15. McConnell, Reilly, and McClean, J. Chem. Phys. 24, 479 (1956).
  16. J. A. Pople, Mol. Phys. 1, 216 (1958).
  17. G. A. Williams and H. S. Gutowsky, J. Chem. Phys. (to be published).
  18. D. M. Grant and M. Karplus (to be published).
  19. Private communication from Frank, Gutowsky, and Anderson, who have measured the fluorine hyperfine splitting in tetra-fluorosemiquinone.
  20. Karplus, Kuppermann, and Isaacson, J. Chem. Phys. 29, 1240 (1958).

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