NMR 3J(C1,H3) couplings in 1-X-bicyclo[1.1.1]pentanes. FPT-DFT and NBO studies of hyperconjugative interactions and heavy atom substituent effects

Verónica Barone, Juan E. Peralta, Rubén H. Contreras

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Abstract

In this work a rationalization of the very large substituent effects on 3J(C1,H3) couplings in 1-X-bicyclo[1.1.1]pentanes is presented. The Fermi contact contribution to such couplings was calculated in a series of 13 X-derivatives within the DFT-B3LYP framework using the finite perturbation theory. Core electrons for atoms beyond the Second Row were taken into account using effective core potentials. Calculated couplings are in very good agreement with experimental values. The role played by hyperconjugative interactions involving bonds or antibonds belonging to the coupling pathway are studied using the NBO approach. Heavy atom contribution to substituent effects on 3J(C1,H3) couplings was estimated as small. This contrasts notably with trends observed in the corresponding 13C substituent chemical shifts, SCSs. The latter were estimated comparing for X = Cl, Br, I, SnMe3, calculated SCSs with their experimental values. Such estimations are in line with explicit calculations of the spin-orbit contribution reported in the literature for smaller compounds.

Original languageEnglish
Pages (from-to)1615-1621
Number of pages7
JournalJournal of Computational Chemistry
Volume22
Issue number14
DOIs
StatePublished - Nov 15 2001

Keywords

  • DFT
  • Fermi contact
  • Heavy atom effect
  • Hyperconjugative interactions
  • NBO

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