Question

Benzene and alkyl-substituted benzenes can be hydroxylated by reaction with H2O2 in the presence of an acidic catalyst. What is the structure of the reactive electrophile? Propose a mechanism for the reaction.

Answer 1

The electrophile is the hydroxide free radical

Step-by-step explanation:

The hydroxylation of benzene and benzene derivatives using hydrogen peroxide proceeds in the presence of an acidic catalyst. The electrophile in this reaction is the hydroxyl free radical generated in an initial step of the reaction.

This is actually a free radical reaction. The hydroxyl radical previously generated reacts with the benzene ring to yield a radical that undergoes further rearrangement to yield the product phenol. The intermediate, shown as part of this reaction mechanism (refer to image attached) is a specie in which the odd electron is delocalized over the entire benzene ring. Loss of a proton completes the reaction mechanism yielding the corresponding phenol.