Unit 18: Reactions of Aromatic Compounds
Beyond EAS, aromatic systems participate in benzylic radical chemistry, benzylic oxidation, selected nucleophilic aromatic substitution, and diazonium-based functional-group interconversion.
- Recognize benzylic positions as unusually reactive because radical and cationic intermediates are resonance-stabilized.
- Predict side-chain oxidation of alkyl benzenes and distinguish it from ring substitution.
- Identify when nucleophilic aromatic substitution becomes feasible on an aryl halide.
- Use diazonium chemistry conceptually as a route from anilines to otherwise hard-to-install substituents.
Checkpoint Questions
- Q: What is the product of toluene treated with hot KMnO4?
- A: Benzoic acid, because the benzylic methyl group is oxidized all the way to a carboxylic acid.
- Q: Why is the benzylic position often favored in radical halogenation?
- A: The benzylic radical is resonance-stabilized by the aromatic ring, lowering the barrier for selective abstraction and substitution.