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Balz-Schiemann Reaction

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The decomposition of aromatic diazonium fluoroborates thermally to yield an aromatic fluoride, boron trifluoride and nitrogen is known as Schiemann reaction.

Balz-Schiemann reaction is named for the German chemists G.Balz and Gunther Robert Arthur Schiemann.

Balz-schiemann Reaction
The preparation of an aryl fluoride starting from an aryl amine fro example aniline and arenediazonium tetrafluoroborate is called the Schieman reaction also called Balz-Schiemann reaction.

Mechanism

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The mechanism for Balz schiemann Reaction is shown below.

Mechanism for Balz Schiemann Reaction

Fluorobenzene is prepared by Balz-Schiemann reaction. It involves the reaction of benzenediazonium chloride with hydrofluoroboric acid (HBF4) to produce fluoborate, which on thermal distortion results in the formation of fluorobenzene.

Balz schiemann Reaction Mechanism

Applications

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The basic Balz-Schiemann reaction involves the preparation of an insoluble arene-diazonium tetrafluoroborate either by direct diazotization or arylamines in aqueous tetrafluorobric acid, or by addition of tetrafluoroboric acid or alkaline tetrafluoroborates to an aqueous solution of another arenediazonium salt.

The synthesis of 4-fluoroestrone used for the visualization f estrogen receptors in breast tumors by positron emission transaxial tomography.

Applications of Balz schiemann Reaction