Downfield Proton Chemical Shifts Are Not Reliable Aromaticity Indicators
2005
Abstract
The downfield chem. shifts of arene hydrogens (delta 1H) are due only in part to the pi ring current contribution [sigma.dblvert.(pi)]; local framework effects are equally important. Neither proton chem. shifts nor even sigma.dblvert.(pi) tensor elements, per se, are reliable aromaticity indicators. Unsatd. polycyclic hydrocarbons with nonarom. quinoid structures have delta 1H and sigma.dblvert.(pi) values in the "arom. range". Conversely, numerous arom. protons, including those in five-membered ring heterocycles, resonate in the "nonarom. range". [on SciFinder (R)]
Details
Title
Downfield Proton Chemical Shifts Are Not Reliable Aromaticity Indicators
Author(s)
Wannere, Chaitanya S. ; Corminboeuf, Clemence ; Allen, Wesley D. ; Schaefer, Henry F. III ; Schleyer, Paul von Rague
Published in
Organic Letters
Volume
7
Issue
8
Pages
1457-1460
Date
2005
Keywords
Density functional theory (PW91; downfield NMR proton chem. shifts are not reliable aromaticity indicators); NMR (chem. shift; downfield NMR proton chem. shifts are not reliable aromaticity indicators); IGLO; Ring current (downfield NMR proton chem. shifts are not reliable aromaticity indicators); Polycyclic compounds Role: PRP (Properties) (hydrocarbons; unsatd.; downfield NMR proton chem. shifts are not reliable aromaticity indicators); Aromaticity (index; downfield NMR proton chem. shifts are not reliable aromaticity indicators); Hydrocarbons Role: PRP (Properties) (polycyclic; unsatd.; downfield NMR proton chem. shifts are not reliable aromaticity indicators); aromaticity indicator downfield nmr proton chem
Note
CAN 142:429747 22-2 Physical Organic Chemistry Center for Computational Chemistry, Department of Chemistry,University of Georgia,Athens,GA,USA. Journal 1523-7060 written in English. 85-01-8 (Phenanthrene); 91-20-3 (Naphthalene); 92-24-0 (Naphthacene); 95-13-6 (1H-Indene); 120-12-7 (Anthracene); 253-01-0 (Cyclobuta[1,2:3,4]dicyclopentene); 257-24-9 (Heptalene); 268-37-1 (2H-Benz[f]indene); 270-53-1 (2H-Indene); 275-51-4 (Azulene); 4026-23-7 (Bicyclo[4.2.0]octa-1,3,5,7-tetraene); 850661-43-7; 850661-44-8 Role: PRP (Properties) (downfield NMR proton chem. shifts are not reliable aromaticity indicators)
Laboratories
LCMD
Record Appears in
Scientific production and competences > SB - School of Basic Sciences > ISIC - Institute of Chemical Sciences and Engineering > LCMD - Laboratory of Computational Molecular Design
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Peer-reviewed publications
Work outside EPFL
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Record creation date
2007-10-22