Concerted Proton–Electron Transfer in Pyridylphenols: The Importance of the Hydrogen Bond

Slowed down by a break up: One-electron oxidation of intramolecularly hydrogen-bonded phenol–pyridine compounds 1 and 2 involves proton transfer coupled with electron transfer (see scheme; B=base). At the same driving force, 2 reacts substantially slower than 1. The methylene group between the phenol and pyridine groups in 2 breaks the conjugation between the rings, which has a marked effect on the hydrogen bond and is likely the origin of the difference in rate constants.