ORGN 90 |
| A series of phenols with an intramolecular hydrogen bond to a pendant pyridine (1a-e) have been prepared and reacted with outersphere one-electron oxidants. These are models for enzymatic electron transfer involving hydrogen-bonded tyrosine residues. Oxidation occurs with concomitant transfer of the phenolic proton to the pyridine via concerted proton-electron transfer (CPET). The nature of the basic moiety and the chemical environment of the proton have substantial effects on the intrinsic barriers to CPET. When the conjugation between the phenol and the pyridine rings is disrupted by a methylene unit (2) the rate constants are substantially slower, by two orders of magnitude at the same driving force. Inclusion of electron donating or withdrawing substituents X on the pyridine also cause significant differences in intrinsic barriers. Correlations between these barriers and proton chemical shifts, electrochemical potentials, X-ray structural data, etc., and insights from DFT calculations will be discussed.
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Physical Organic Chemistry: Calculations, Mechanisms, Photochemistry, and High-Energy Species
1:00 PM-5:20 PM, Sunday, 10 September 2006 Moscone Center -- Room 133, Oral
Division of Organic Chemistry |
