Keto–enol and enol–enol tautomerism in trifluoromethyl-β-diketones

A variety of trifluoromethyl-β-diketones were investigated using 1H, 13C, 19F NMR, IR and UV–vis spectrophotometry in nonpolar solvents. In general, spectral evidence indicates the β-diketones exist as mixtures of two chelated cis-enol forms. IR and UV–vis spectrophotometry show the enol–enol equili...

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Bibliographic Details
Published in:Journal of fluorine chemistry 2006-06, Vol.127 (6), p.780-786
Main Authors: Sloop, Joseph C., Bumgardner, Carl L., Washington, Gary, Loehle, W. David, Sankar, Sabapathy S., Lewis, Adam B.
Format: Article
Language:English
Subjects:
19F NMR
Chelated-OH
Enol
Enone
Tautomerism
β-Diketone
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Summary:A variety of trifluoromethyl-β-diketones were investigated using 1H, 13C, 19F NMR, IR and UV–vis spectrophotometry in nonpolar solvents. In general, spectral evidence indicates the β-diketones exist as mixtures of two chelated cis-enol forms. IR and UV–vis spectrophotometry show the enol–enol equilibrium lies in the direction of enol form a, which maximizes conjugation in most cases. ▪ The keto–enol (K⇌E) and enol–enol (E⇌E) equilibria of a variety of trifluoromethyl-β-diketones were investigated using 1H, 13C, 19F NMR spectroscopy, infrared spectroscopy and ultraviolet-visible spectrophotometry in nonpolar solvents. In general, NMR, IR and UV spectral evidence indicates that trifluoromethyl-β-diketones exist as mixtures of two chelated cis-enol forms in nonpolar media. Infrared spectroscopy and ultraviolet spectrophotometry show the E⇌E equilibrium lies in the direction of the enol form which maximizes conjugation in most cases. Exceptions are noted and discussed.
ISSN:0022-1139
1873-3328
DOI:10.1016/j.jfluchem.2006.02.012