Electron spin resonance studies. Part XXVIII. Oxidation of enols, enol ethers, and related compounds with the hydroxyl and the amino-radical

Abstract

The reactions of some enols and enol ethers with the hydroxyl and the amino-radical have been investigated by e.s.r. spectroscopy. Adducts from enols with the hydroxyl radical, but not apparently the amino-radical, undergo acid-catalysed elimination of water. Evidence is adduced that the two adducts from an enol ether with the hydroxyl radical, but again not the amino-radical, undergo acid-catalysed interconversion, presumably by way of an oxonium ion; results from the oxidation of 2-methoxyethanol and 1,2-dimethoxyethane with the hydroxyl radical are helpful in elucidating the significance of this rearrangement. A further inference from the results is that the radical MeO·CH(OH)·CH₂· is thermodynamically more stable than its alkoxy-conjugated isomer ·CH(OMe)·CH₂OH, at least in aqueous acid, and the basis for this is discussed.