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Chemistry · Glossary

What is Nucleophilic aromatic substitution?

Also known as: Meisenheimer complex

Definition 29.7 University Chemistry — Year 3 · Chapter 29 — Heterocyclic Chemistry

Nucleophilic aromatic substitution (SNAr\mathrm S_\mathrm NAr) replaces a leaving group on an electron-poor aromatic ring by a nucleophile, through addition followed by elimination. The anionic addition intermediate is a Meisenheimer complex.

Nucleophilic substitution of 2-chloropyridine: the nucleophile adds to C2, giving an anionic intermediate whose negative charge sits largely on the ring nitrogen (one resonance structure shown); chloride then leaves and the aromatic ring is restored.
Nucleophilic substitution of 2-chloropyridine: the nucleophile adds to C2, giving an anionic intermediate whose negative charge sits largely on the ring nitrogen (one resonance structure shown); chloride then leaves and the aromatic ring is restored.
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