ISSN:
0749-1581
Keywords:
1H NMR
;
13C NMR
;
19F NMR
;
β-Diketones
;
Tautomerism
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Multinuclear NMR experiments on fluorinated β-diketones have furnished information on the various tautomers present in solution and their proportions. 2-Trifluoroacetyl-1-indalone in CDCI3 solution exists in the enol form, as a mixture of exocyclic and endocyclic cis-enols with the exocyclic form favoured, but in DMF-d7 solution the equilibrium shifts to 40% enol, 60% hydrate with the enol and hydrate being in slow exchange on the NMR time scale. 2-Trifluoroacetyl-1-tetralone in CDCI3 solution exists only as the enol forms, approximately equally populated, but in DMF-d7, unlike the indalone, no hydrate is formed although there is now 6% of the keto form present in slow exchange. The experimental results were compared with calculated data produced using molecular orbital simulations. These agree with the NMR results and predict that the tetralone enol tautomers are both significantly populated at room temperature but that the indalone exists primarily as the exocyclic enol. The oxygen-oxygen internuclear distance in the hydrogen bond was estimated from the OH proton chemical shift based on a calibration from solid-state data from model compounds, and agrees well with the predictions using the molecular mechanics approach.
Additional Material:
2 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260280716
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