Sandmaeyer's Reaction - benzene diazonium salt

Replacement reaction of benzene diazonium chloride by halide ion

When the solution of freshly prepared benzene diazonium salt is trated with a mixture of cuprous chloride or cuprous bromide in presence of concentrated HCL or HBr, we get chlorobenzene or bromobenzene. This reaction is known as Sandmaeyer's reaction.

Alternatively the same reaction can be done by copper powder and cone. HX instead of cuprous halide and this modified reaction is called Gatterman reaction.

Indobenzene can be prepared from benzene diazonium salt by reacting with KI solution.
Replacement with fluoride is known as Balz Schiemann reaction.In this benzene diazonium salt is reacted with fluoroboric acid heated to get fluorobenzene.
Preparation of aryl halides from diazonium salt by replacement gives pure aryl halides and provides important synthetic route for preparation of aryl iodides and aryl fluorides.


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