Solvent-induced isotope effects in NMR spectroscopy. A study of hydrogen bonding between the carbonyl group in chalcone and trifluoracetic acid (TFA-d or TFA) in chloroform solution
✍ Scribed by Lech Kozerski
- Publisher
- John Wiley and Sons
- Year
- 1982
- Tongue
- English
- Weight
- 397 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Splittings, 6,, were observed for each carbon atom, C,, of chalcone in spectra obtained from coaxial 5 and 10 mm NMR sample tubes containing solutions equimolar in the concentration of the ketone and of TFA or TFA-d as hydrogen-bond donors, respectively. It was found that a linear expression, S,A,+x,S,(D,H) relates these splittings, S,, induced by the isotopic substitution in a hydrogen bond, to the parameter A,, denoting the change in chemical shift for each carbon site in complexed and free ketone, and S,(D, H), the solvent-induced isotope effect in a complex. The origin of the phenomenon is briefly discussed. It is also shown that the secondary deuterium isotope effect can give the same information about the form of the potential energy well in the hydrogen-bond as the primary H/D isotopte shifts.