NDLI: Is the Conventional Interpretation of the Anisotropic Effects of CC Double Bonds and Aromatic Rings in NMR Spectra in Terms of the π-Electron Shielding/Deshielding Contributions Correct?

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Baranac-stojanovic, Marija Koch, Andreas Kleinpeter, Erich
Description	Author Affiliation: Baranac-Stojanovic M ( Faculty of Chemistry, University of Belgrade, Studentski trg 16, P.O.Box 158, 11000 Belgrade, Serbia. mbaranac@chem.bg.ac.rs)
Abstract	Based on the nucleus-independent chemical shift (NICS) concept, isotropic magnetic shielding values have been computed along the three Cartesian axes for ethene, cyclobutadiene, benzene, naphthalene, and benzocyclobutadiene, starting from the molecular/ring center up to 10 Å away. These through-space NMR spectroscopic shielding (TSNMRS) values, which reflect the anisotropic effects, have been broken down into contributions from localized- and canonical molecular orbitals (LMOs and CMOs); these contributions revealed that the proton NMR spectroscopic chemical shifts of nuclei that are spatially close to the CC double bond or the aromatic ring should not be explained in terms of the conventionally accepted π-electron shielding/deshielding effects. In fact, these effects followed the predictions only for the antiaromatic cyclobutadiene ring.
ISSN	09476539
e-ISSN	15213765
Journal	Chemistry - A European Journal
Issue Number	1
Volume Number	18
Language	English
Publisher	Wiley-VCH;ChemPubSoc Europe
Publisher Date	2012-01-02
Publisher Place	Germany
Access Restriction	Open
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Organic Chemistry Catalysis

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Is the Conventional Interpretation of the Anisotropic Effects of CC Double Bonds and Aromatic Rings in NMR Spectra in Terms of the π-Electron Shielding/Deshielding Contributions Correct?