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Stereochemical dependence of NMR geminal spin–spin coupling constants
Author(s) -
Contreras Rubén H.,
Provasi Patricio F.,
dos Santos Francisco P.,
Tormena Cláudio F.
Publication year - 2009
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.2359
Subject(s) - geminal , chemistry , antibonding molecular orbital , coupling constant , natural bond orbital , fermi contact interaction , spin (aerodynamics) , propagator , computational chemistry , atomic orbital , crystallography , hyperfine structure , stereochemistry , density functional theory , atomic physics , quantum mechanics , thermodynamics , electron , physics
In this work it was sought to explore the versatility of geminal spin–spin coupling constants, 2 J XY SSCCs, as probes for stereochemical studies. A set of compounds, where their experimental 2 J XY SSCCs through the X–C–Y molecular fragment are predicted to be sensitive to hyperconjugative interactions involving either bonding or antibonding orbitals containing the C carbon atom (‘coupling pathway’), were analyzed. SSCC calculations were performed for some selected examples using the second order polarization propagator approximation (SOPPA) method or within the DFT‐B3LYP framework. Hyperconjugative interactions were calculated within the Natural Bond Orbital (NBO) approach. Results are condensed in two qualitative rules: Rule I M —hyperconjugative interactions transferring charge into the coupling pathway yield a positive increase to the Fermi contact (FC), contribution to 2 K XY reduced spin–spin coupling constants (RSSCC), and Rule II M —hyperconjugative interactions transferring charge from the coupling pathway yield a negative increase to the FC contribution to 2 K XY RSSCC. Copyright © 2008 John Wiley & Sons, Ltd.