Question

Replacement of the diazonium group by halogen in presence of copper powder is:

• A. Gabriel reaction
• B. Gattermann reaction
• C. Hofmann reaction
• D. Sandmeyer reaction

Answer 1

The Correct Option is D

To solve the question about the replacement of the diazonium group by halogen in the presence of copper powder, we need to understand the reactions in the context of organic chemistry.

Let's look at the options provided:

• Gabriel Reaction: This is primarily used for the synthesis of primary amines and does not involve diazonium groups or halogens.
• Gattermann Reaction: This involves the introduction of a formyl group (CHO) into aromatic compounds and uses a mixture of HCN and HCl in the presence of a Lewis acid, such as AlCl₃. It does not specifically involve diazonium groups being replaced by halogens.
• Hofmann Reaction: This is used to convert amides to amines, with the loss of one carbon atom. It does not involve copper powder or diazonium groups.
• Sandmeyer Reaction: This is a reaction where an aryl diazonium compound is transformed into an aryl halide using copper(I) chloride or copper(I) bromide. The reaction indeed involves the replacement of the diazonium group with a halogen in the presence of copper (or copper salts), making it the correct answer.

Conclusion: The correct answer is the Sandmeyer reaction. In this reaction, copper powder or copper salts are used to facilitate the replacement of the diazonium group by a halogen.

This reaction is valuable in the preparation of aryl halides from anilines, where initially, the amine group is converted into a diazonium salt, and then further treated with halide ions in the presence of copper to produce the desired aryl halide.