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Structural Chemistry

, Volume 27, Issue 2, pp 671–679 | Cite as

Essential versus accidental isochrony of diastereotopic nuclei in NMR spectroscopy

  • Ibon Alkorta
  • José Elguero
Original Research

Abstract

Compounds where a non-stereogenic sp 2 atom (for instance the C atom of a benzene ring) is linked to a stereogenic sp 3 atom (for instance CHFCl) have several conformations where two diastereotopic nuclei become isochronous. This also happens in some cases when the sp 3 atom is non-stereogenic, the difference being related to the weighted value of the difference of absolute shieldings. The results here described seem to be in contradiction with experimental results pointing out that all diastereotopic nuclei are anisochronous. Two examples of typical diastereotopic nuclei involving C(sp 3)–C(sp 3) bonds, a propane and an ethane, were also discussed.

Keywords

Isochrony Anisochrony Enantiotopicity Diastereotopicity Absolute shieldings GIAO 

Notes

Acknowledgments

Thanks are also given to the Ministerio de Economía y Competitividad of Spain (Project CTQ2012-13129-C02-02) and the Comunidad Autónoma de Madrid (Project Fotocarbon, S2013/MIT-2841). We warmly thank Professors Hans-Heinrich Limbach, Alain Fruchier, and Christian Roussel for invaluable comments on previous versions of this paper as well as one of the reviewers who suggested that we compare diastereotopicity and differences in energy.

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Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  1. 1.Instituto de Química Médica (CSIC)MadridSpain

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