alleryThe **Balz–Schiemann reaction** converts $ArN_2^+$ to $ArF$ via which intermediate?
A$ArOH + HF$
B$ArN_2^+ BF_4^-$ (then $\Delta$)
C$ArMgBr + F_2$
D$ArN_2^+ Cl^- + AgF$
Answer & Solution
Correct answer: B. $ArN_2^+ BF_4^-$ (then $\Delta$)
$ArN_2^+Cl^- + HBF_4 \to ArN_2^+BF_4^-\downarrow$.
The dry tetrafluoroborate salt, on gentle heating, decomposes to $ArF + N_2\uparrow + BF_3$.
The only practical lab route to aryl fluorides from amines.
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