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Balz-Schiemann Reaction

April 13, 2013

Balz-Schiemann Reaction is also called Schiemann reaction which describes the preparation of an aromatic fluoborate followed by its thermal decomposition to afford the corresponding aryl fluoride. This reaction is named after German chemists Günther Schiemann and Günther Balz.

 

Balz–Schiemann reaction

Balz-Schiemann Reaction is also called Schiemann reaction which describes the preparation of an aromatic fluoborate followed by its thermal decomposition to afford the corresponding aryl fluoride. This reaction is named after German chemists Günther Schiemann and Günther Balz.

Balz–Schiemann reaction

Diazotization of the appropriate aromatic amines with nitrous acid followed by addition of fluoroboric acid gives the corresponding aryl diazonium salts. Thermal decomposition of the dry aryl diazonium salts gives aryl fluoride.

Mechanism of the reaction

  • Sodium nitrite and aqueous acid generates nitrous acid further undergo dehydration to form nitrosyl cation.
  • Reaction of nitrosyl cation with aryl amine eventually affords the aryl diazonium salt after tautomerization and dehydration.
  • The addition of fluoroboric acid sets for the second atep leading to aryl fluoride.

Balz–Schiemann reaction mechanism

Example

Predict the mechanism of the following reaction

Balz–Schiemann reaction example

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