Fischer–Hepp rearrangement

Fischer–Hepp rearrangement

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Mechanism of the Fischer–Hepp rearrangement

The Fischer–Hepp rearrangement is a chemical reaction that involves the migration of a nitroso group from the nitrogen atom of an aromatic amine to the ortho or para position of the aromatic ring. This rearrangement is named after the German chemists Emil Fischer and Otto Hepp, who first described the reaction in 1886.

Mechanism

The mechanism of the Fischer–Hepp rearrangement involves the formation of a nitrosamine intermediate. The reaction typically proceeds under acidic conditions, where the nitroso group is protonated, facilitating its migration to the aromatic ring. The rearrangement can be represented as follows:

1. Formation of a nitrosamine intermediate from the reaction of an aromatic amine with a nitrosating agent. 2. Protonation of the nitrosamine, leading to the formation of a more reactive species. 3. Migration of the nitroso group to the ortho or para position of the aromatic ring, resulting in the formation of a nitrosoarene.

Applications

The Fischer–Hepp rearrangement is used in the synthesis of various aromatic compounds, particularly in the preparation of nitroso derivatives of anilines. These compounds are valuable intermediates in the synthesis of dyes, pharmaceuticals, and agrochemicals.

Related reactions

The Fischer–Hepp rearrangement is related to other rearrangement reactions involving nitroso groups, such as the Beckmann rearrangement and the Hofmann rearrangement. These reactions also involve the migration of functional groups under specific conditions.

Related pages

• Emil Fischer
• Otto Hepp
• Nitrosamine
• Aromatic amine
• Rearrangement reaction