Synthetic Uses of Aryl Diazonium Salts

• Synthetic Uses of Aryl Diazonium Salts: This salts (Ar-N₂⁺X⁻) are versatile intermediates in organic synthesis, particularly in the synthesis of aromatic compounds.

Benzenediazonium cation

Key Reactions: Synthetic Uses of Aryl Diazonium Salts:

1. Sandmeyer Reaction:

   • It can be converted to aryl halides (Ar-Cl, Ar-Br, Ar-CN) by treating them with corresponding copper(I) salts like CuCl, CuBr, or CuCN.
   • This reaction is useful for introducing halogens or cyano groups into the aromatic ring.

2. Gattermann Reaction:

   • Similar to the Sandmeyer reaction but specifically used to introduce a formyl group (-CHO) into the aromatic ring.

3. Diazo Coupling:

   • It reacts with phenols or aromatic amines to form azo compounds (Ar-N=N-Ar’), which are often brightly colored and used in dyes.

4. Reduction:

   • Aryl diazonium salts can be reduced to the corresponding aryl hydrides (Ar-H) using hypophosphorous acid (H₃PO₂) or other reducing agents.

5. Schiemann Reaction:

   • It can be fluorinated to form aryl fluorides (Ar-F) by treating with fluoroboric acid (HBF₄), followed by thermal decomposition.

6. Replacement by Hydroxyl Group:

   • Aryl diazonium salts can be hydrolyzed to phenols (Ar-OH) by heating with water.

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