Sandmeyer Reaction

Sandmeyer reaction is a type of radical-nucleophilic aromatic substitution reaction. It is a useful tool by which an amino group on an aromatic ring is replaced with different substituents. During the Sandmeyer reaction, the amino group is converted into a diazonium salt that can be transformed into various functional groups using a catalyst. The mechanism involves several steps, including the generation of intermediary compounds.

Example of Sandmeyer Reaction
Mechanism of Sandmeyer Reaction

Step 1: Protonation takes place twice during which sodium nitrite reacts with hydrogen halide to form nitrosonium and halide ions

Step 2: Conversion of amine into diazonium salt by the electrophilic nitrosonium

Step 3: Single electron transfer from copper to the diazonium and from halide to copper (I) halide ion to form a neutral diazo radical and copper (II) halide

Step 4: Release of nitrogen gas by the diazo radical to form an aryl radical which reacts with the copper (II) halide to regenerate copper (I) halide catalyst and form the final aryl halide product

Applications of Sandmeyer Reaction

• Halogenation - Synthesis of aryl halides
• Cyanation - Synthesis of benzonitriles and other useful medicinal drugs
• Trifluoromethylation - Synthesis of aryl compounds having trifluoromethyl group and are used as pharmaceuticals
• Hydroxylation - Conversion of aryl amines into phenols