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Interpretation of vicinal proton–proton coupling constants of heteroaromatic molecules in terms of topological electron density descriptors
Author(s) -
SánchezMendoza Ernesto,
HernándezTrujillo Jesús
Publication year - 2010
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2679
Subject(s) - chemistry , vicinal , proton , coupling constant , fermi contact interaction , delocalized electron , thiophene , pyrrole , furan , computational chemistry , molecule , electron , coupling (piping) , molecular physics , quantum mechanics , physics , organic chemistry , mechanical engineering , engineering
The indirect vicinal proton–proton coupling constants for pyrrole, furan, thiophene and 15 related heteroaromatic compounds were calculated using the Khon–Sham approximation. An analysis of the four Ramsey contributions to the coupling constants was carried out showing that the Fermi contact term is always positive and dominant, although the remaining contributions have a nonnegligible net negative contribution. The trends observed for the proton–proton coupling constants were rationalized in terms of the properties of the electron density. It was found that electron delocalization between the corresponding hydrogen atoms plays a major role on the observed behavior with the charges of the carbon atoms bonded to them and the accompanying geometric variations being also of importance in the coupling mechanism. Copyright © 2010 John Wiley & Sons, Ltd.