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8686546 
Journal Article 
Keto-Enol Equilibrium in 1, 3-Cyclohexanediones 
Yogev, A; Mazur, Y 
1967 
Yes 
Journal of Organic Chemistry
ISSN: 0022-3263
EISSN: 1520-6904 
32 
7 
2162-2166 
English 
The ultraviolet and nmr spectra of dimedone (I) and 1, 3-cyclohexanedione (II) were measured in different solvents at various concentrations. In cyclohexane and chloroform solutions, at very high dilutions, the keto forms of I and II exist in equilibrium with the respective monomeric enol forms. With gradual increase of the concentrations, the dimeric enol form becomes dominant, and at still higher concentrations higher degrees of association of the enol form are observed. The proton and 17O nmr measurements of dimedone (I) at room temperature point to a fast intermolecular hydrogen transfer in the enol form, and to a rapid interconversion of the two conformers Ia and Ib. Lowering of the temperature results in slower interconversion of the two conformers. The activation energy for this process was calculated to be 4.1 ± 0.5 kcal/mole. 1967, American Chemical Society. All rights reserved.