Elsevier

Journal of Molecular Structure

Volume 161, October 1987, Pages 193-204
Journal of Molecular Structure

β-diketone interactions: Part 5. Solvent effects on the keto ⇋ enol equilibrium

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Abstract

The keto ⇋ enol equilibrium of pentane-2,4-dione (PD) has been measured in 21 solvents at infinite dilution and a linear free energy relationship (LFER) tested against four solvent polarity vectors: ϵ, ET, π* and A + B. The best correlation coefficient is found for A + B. Similarly 3-methyl-pentane-2,4-dione (MePD) has been studied in 14 solvents and 3-ethylpentane-2,4-dione (EtPD) in six. The results suggest that the cyclic hydrogen bonding of the enol remains intact in all the solvents studied.

References (35)

  • L.W. Reeves

    Can. J. Chem.

    (1957)
  • A.I. Vogel
  • V. Gutman
    (1968)
  • E. Grundwald et al.

    J. Am. Chem. Soc.

    (1948)
  • S. Winstein et al.

    J. Am. Chem. Soc.

    (1951)
  • A.H. Fainberg et al.

    J. Am. Chem. Soc.

    (1956)
  • E.M. Kosower

    J. Am. Chem. Soc.

    (1958)
  • E.M. Kosower
  • E.M. Kosower

    J. Chem. Phys.

    (1964)
  • K. Dimroth et al.

    Liebig Ann. Chem.

    (1983)
  • K. Dimroth et al.

    Liebig Ann. Chem.

    (1963)
  • M.J. Kamlet et al.

    J. Am. Chem. Soc.

    (1976)
    M.J. Kamlet et al.

    J. Am. Chem. Soc.

    (1976)
  • R.W. Taft et al.

    J. Am. Chem. Soc.

    (1985)
  • C.G. Swain et al.

    J. Am. Chem. Soc.

    (1983)
  • J. Emsley et al.

    J. Chem. Soc. Perkin Trans. I

    (1986)
  • J. Emsley et al.

    J. Chem. Soc. Perkin Trans. II

    (1986)
  • J. Emsley et al.

    J. Mol. Struct.

    (1987)
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