Hyperconjugation effects of hydroxyl and amine groups on chemical shifts of neighboring carbon nuclei

Systematic investigations of conformational effects of the hydroxyl group on carbon or hydrogen chemical shifts of different types of alcohols reveal that, besides stereoelectronic effects, hyperconjugation with lone pairs may have a strong influence. In view of the growing use of chemical shifts in...

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Veröffentlicht in:International journal of quantum chemistry 2003, Vol.95 (3), p.322-328
Hauptverfasser: De M. Carneiro, José Walkimar, Dias, Jacques F., Tostes, José Glauco R., Seidl, Peter R., Taft, Carlton A.
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Sprache:eng
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Zusammenfassung:Systematic investigations of conformational effects of the hydroxyl group on carbon or hydrogen chemical shifts of different types of alcohols reveal that, besides stereoelectronic effects, hyperconjugation with lone pairs may have a strong influence. In view of the growing use of chemical shifts in probing the structure of biologic molecules, we employed DFT/GIAO/NBO calculations at the B3LYP level for conformers obtained from partial optimization of structures resulting from 30° variations of the CCXH (XO, N) dihedral angles to verify if nitrogen responded in a fashion similar to oxygen. Although the hybridization and geometry of hydroxyl and amine groups are distinct, the lone pair on nitrogen reveals hyperconjugation with suitably positioned orbitals on alkyl groups. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 95: 322–328, 2003
ISSN:0020-7608
1097-461X
DOI:10.1002/qua.10760