Question

Fluorobenzene $\left(C_6{H}_{5}F\right)$ can be synthesised in the lab:

• A. by heating phenol with HF and KF
• B. from aniline by diazotization followed by heating the diazonium salt with $HB{F}_4$
• C. by direct fluorination of benzene with $F_2$ gas
• D. by reacting bromo benzene with NaF solution

Answer 1

The correct option is B from aniline by diazotization followed by heating the diazonium salt with $HB{F}_4$

Benzene undergoes diazotization to home benzenediazonium salt.

when fluoroboric acid is added to the solution of diazonium salt of precipitate of diazonium fluoroborate is obtained, which is filtered filtered and dried. dry diazonium fluoroborate on heating decomposes to give fluorobenzene. This reaction is called balz Schiemann reaction.

$C_6{H}_5-N_2^{+}{X}^{-}$ + $HB{F}_4$ $\to$ $C_6{H}_5-N_2^{+}B{F}_4^{-}$ $\to$ $C_6{H}_5-F$ + $B{F}_3$ + $N_2\uparrow$