Question

Which among the following is true for Balz–Schiemann reaction?

• A. In this Ar–Cl is obtained from Ar–\(\text{N}_2^+X^-\)
• B. It is useful for preparation of nitrobenzene from benzene diazonium salts
• C. In this Ar–CN is obtained from Ar–\(\text{N}_2^+X^-\)
• D. In this Ar–F is obtained from Ar–\(\text{N}_2^+X^-\)

Hint:

Balz–Schiemann reaction is the only reliable method to prepare aryl fluorides.

Answer 1

The Correct Option is D

Step 1: Define Balz–Schiemann reaction.
Balz–Schiemann reaction is used for preparation of aryl fluorides from aromatic diazonium salts.
Step 2: Reaction involved.
Aromatic diazonium tetrafluoroborate decomposes on heating to give aryl fluoride: \[ \text{ArN}_2^+\text{BF}_4^- \xrightarrow{\Delta} \text{Ar–F} + \text{BF}_3 + \text{N}_2 \] Step 3: Eliminate incorrect options.
Ar–Cl and Ar–CN are formed by Sandmeyer reaction, not Balz–Schiemann reaction.
Step 4: Conclusion.
Hence, Ar–F is obtained from diazonium salts in Balz–Schiemann reaction.