Benzene diazonium fluoroborate heated with aqueous sodium nitrite in presence of copper gives:

Question

Accepted Answer

Benzene diazonium fluoroborate, when heated with aqueous sodium nitrite in the presence of copper, undergoes a chemical reaction known as the Sandmeyer reaction. This reaction is a well-known method for introducing a nitro group into an aromatic ring, resulting in the formation of nitrobenzene. Let's explore why Option 3, nitrobenzene, is the correct answer and why the other options are incorrect.

1. **Explanation for Option 3 (Nitrobenzene):**
   - The Sandmeyer reaction involves the conversion of diazonium salts into various substituted aromatic compounds. In this specific case, the presence of sodium nitrite and copper facilitates the replacement of the diazonium group with a nitro group. This results in the formation of nitrobenzene. The copper acts as a catalyst, promoting the transfer of the nitro group to the benzene ring. Therefore, the correct product of this reaction is nitrobenzene, making Option 3 the correct answer.

2. **Why Option 1 (Fluorobenzene) is incorrect:**
   - Fluorobenzene is typically formed through the Balz-Schiemann reaction, where a diazonium salt is decomposed in the presence of fluoroboric acid or other fluorinating agents. The reaction conditions described in the question do not favor the formation of fluorobenzene, as sodium nitrite and copper are not suitable for introducing a fluorine atom into the aromatic ring.

3. **Why Option 2 (Aniline) is incorrect:**
   - Aniline is the parent amine from which diazonium salts are derived. The conversion of a diazonium salt back to aniline would require reduction, not the conditions provided in the question. The presence of sodium nitrite and copper does not facilitate the reduction of the diazonium group back to an amine.

4. **Why Option 4 (p-amino azobenzene) is incorrect:**
   - p-Amino azobenzene is typically formed through azo coupling reactions, where a diazonium salt reacts with an aromatic amine. The conditions described in the question do not involve an aromatic amine or the necessary conditions for azo coupling. Therefore, the formation of p-amino azobenzene is not possible under the given reaction conditions.

In conclusion, the reaction of benzene diazonium fluoroborate with aqueous sodium nitrite in the presence of copper leads to the formation of nitrobenzene, supporting Option 3 as the correct answer.