13C chemical shifts and nJCH coupling constants have been determined both experimentally (by means of J-resolved NMR spectroscopy) and theoretically (by DFT calculations) for a series of organic molecules. With the exception of halogen-bonded carbon nuclei, a good correlation is observed between experimental and calculated data. The magnitude of the most important contributions to the spin-spin coupling constant (Fermi-contact, diamagnetic and paramagnetic spin-orbit contributions) have been determined. The spin-orbit terms are negligible or cancel out (1JCH and 3JCH), thus leaving the contact term as the only relevant contribution, but become important for 2JCH in aromatic (but not in aliphatic) compounds. Relativistic effects on the 13C chemical shift of carbon bonded to a fairly heavy atom (bromine) have also been investigated. Finally, conformational effects on the long-range nJCH coupling constants has been investigated in a model alkane derivative (n-butyl chloride). The implications to structure prediction and determination by NMR are discussed.

Predicting C-13 NMR spectra by DFT calculations

BAGNO, ALESSANDRO;RASTRELLI, FEDERICO;SAIELLI G.
2003

Abstract

13C chemical shifts and nJCH coupling constants have been determined both experimentally (by means of J-resolved NMR spectroscopy) and theoretically (by DFT calculations) for a series of organic molecules. With the exception of halogen-bonded carbon nuclei, a good correlation is observed between experimental and calculated data. The magnitude of the most important contributions to the spin-spin coupling constant (Fermi-contact, diamagnetic and paramagnetic spin-orbit contributions) have been determined. The spin-orbit terms are negligible or cancel out (1JCH and 3JCH), thus leaving the contact term as the only relevant contribution, but become important for 2JCH in aromatic (but not in aliphatic) compounds. Relativistic effects on the 13C chemical shift of carbon bonded to a fairly heavy atom (bromine) have also been investigated. Finally, conformational effects on the long-range nJCH coupling constants has been investigated in a model alkane derivative (n-butyl chloride). The implications to structure prediction and determination by NMR are discussed.
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

Caricamento pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2466643
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 127
  • ???jsp.display-item.citation.isi??? 125
social impact