Acidities of Stable Simple Enols and Bond Dissociation Enthalpies of Their H−O Bonds in DMSO

The pK HA values for eight stable enols and the oxidation potentials of their anions, E ox(A-), were determined in DMSO, and the bond dissociation enthalpies (BDE) of their O−H bonds were estimated using the equation, BDEHA = 1.37pK HA + 23.1E ox(A-) + 73.3 kcal/mol (1). For Mes2CC(OH)R enols the p...

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Bibliographic Details
Published in:Journal of organic chemistry 1997-08, Vol.62 (16), p.5371-5373
Main Authors: Bordwell, F. G, Zhang, Shizhong, Eventova, Irina, Rappoport, Zvi
Format: Article
Language:English
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Summary:The pK HA values for eight stable enols and the oxidation potentials of their anions, E ox(A-), were determined in DMSO, and the bond dissociation enthalpies (BDE) of their O−H bonds were estimated using the equation, BDEHA = 1.37pK HA + 23.1E ox(A-) + 73.3 kcal/mol (1). For Mes2CC(OH)R enols the pK HA's increase with the bulk of R from 17.8 for R = H to 19.9 for R = t-Bu; the E ox(A-) values become more negative, and the BDEs decrease from 82.2 kcal/mol for R = H to 78.3 for R = t-Bu. The pK HA values roughly parallel the association constants of the enols with the DMSO solvent. These values are discussed in terms of steric and electronic effects.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo970404i