Question

In the reaction :

P,Q and R respectively are :

• A. NaNO₂ + dil.HCl, HBF₄, Cu + NaNO₂
• B. NaNO₂ + con.HCl, F₂, Cu + NaNO₃
• C. NaNO₂ + dil.HCl, BF₃, Cu + NaNO₂
• D. NaNO₃ + dil.HCl, F₂, Cu + NaNO₃

Answer 1

The Correct Option is A

In the given reaction sequence, the steps can be broken down as follows:

The starting compound has an amine group (NH₂) attached to a benzene ring.

In the first step, the amine group undergoes diazotization, where it reacts with NaNO₂ and dilute HCl to form the diazonium salt (P).

In the second step, the diazonium salt reacts with BF₃, leading to the formation of Q.

In the third step, the diazonium compound (Q) is reacted with Cu and NaNO₂, resulting in the formation of R, which is a nitro group (NO₂) attached to the benzene ring.

Conclusion:

The correct sequence of reactions corresponds to Option C:

P is the diazonium salt formed with NaNO₂ and dilute HCl.

Q is the intermediate after reacting with BF₃.

R is the final product after reacting with Cu and NaNO₂, which is a nitrobenzene.

Thus, the answer is Option C.

Answer 2

The reaction in the question is a typical diazotization reaction followed by the Sandmeyer reaction. 

Step 1: Diazotization (P to Q): The amine group (-NH₂) on the benzene ring reacts with sodium nitrite (NaNO₂) in the presence of dilute HCl to form the diazonium salt (C₆H₅–N₂Cl). This is the diazotization step. 

Step 2: Sandmeyer Reaction (Q to R): The diazonium salt (C₆H₅–N₂Cl) then undergoes the Sandmeyer reaction. In this case, the reaction occurs in the presence of copper (Cu) and sodium nitrite (NaNO₂) to substitute the diazonium group with a nitro group (-NO₂) to form the final product (C₆H₅–NO₂). 

Thus, the correct reagents for the reaction are NaNO₂ + dil. HCl for the diazotization and Cu + NaNO₂ for the Sandmeyer reaction, making option (A) the correct answer.