REACTIONS OF ALKOXY RADICALS: I. HYDROGEN ATOM ABSTRACTION FROM SUBSTITUTED TOLUENES

Abstract

The relative rates of hydrogen atom abstraction from ten substituted toluenes by t-butoxy radicals in carbon tetrachloride at 40 °C have been measured and the data fitted to the Hammett equation. A much better correlation is obtained with the σ+ constants than with the σ constants of the substituents. In this respect, therefore, the reaction is similar to the majority of hydrogen atom abstraction reactions by radicals of moderate and high electron affinity. That is, the polar properties of the substituents are much more important than their stabilizing effect on the benzyl radical formed in the reaction.The cumyloxy radical has a similar reactivity to the t-butoxy radical. The p-nitrocumyloxy radical appears to be slightly more reactive and also slightly more susceptible to the polar effects of substituents than are t-butoxy or cumyloxy radicals.