Protonenresonanzspektren von aromatischen N‐Oxiden Berechnung der chemischen Verschiebungen, verursacht durch die Feldeffekte der N-O‐gruppe

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Abstract
The proton NMR. spectra of a series of aromatic amines, their N‐oxides and the corresponding protonated species are analysed. The results for different protons are expressed in terms of differential chemical shifts of the N‐oxide with respect to the corresponding amine or to the hydrocarbon. These data are compared with calculated shielding values obtained according to the theories of McConnell & Buckingham using published data for the magnetic susceptibilities and electric dipoles of the functional groups. The major part of the shielding by the N‐oxide group originates from the electric dipole. If one considers resonance structures for the aromatic N‐oxides the single bond structure and the double bond structure for the NO bond are of approximately equal importance.