Aryl diazonium salts (Ar-N₂⁺X⁻) are versatile intermediates in organic synthesis, particularly in the synthesis of aromatic compounds.
Key Reactions of Aryl Diazonium Salts:
Sandmeyer Reaction:
Aryl diazonium salts 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.
Gattermann Reaction:
Similar to the Sandmeyer reaction, but specifically used to introduce a formyl group (-CHO) into the aromatic ring.
Diazo Coupling:
Aryl diazonium salts react with phenols or aromatic amines to form azo compounds (Ar-N=N-Ar'), which are often brightly colored and used in dyes.
Reduction:
Aryl diazonium salts can be reduced to the corresponding aryl hydrides (Ar-H) using hypophosphorous acid (H₃PO₂) or other reducing agents.
Schiemann Reaction:
Aryl diazonium salts can be fluorinated to form aryl fluorides (Ar-F) by treating with fluoroboric acid (HBF₄), followed by thermal decomposition.
Replacement by Hydroxyl Group:
Aryl diazonium salts can be hydrolyzed to phenols (Ar-OH) by heating with water.