✍ Scribed by Rubén H. Contreras; Patricio F. Provasi; Francisco P. dos Santos; Cláudio F. Tormena
No coin nor oath required. For personal study only.
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.
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