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Fluorobenzene\[({C_6}{H_5}F)\] can be synthesized in the laboratory:
(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 bromobenzene with \[NaF\] solution

Last updated date: 13th Jun 2024
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Hint: As we know that the fluorine atom is very small in size and also is an electron rich atom and\[{F_2}\] gas is very explosive in nature so if we use fluorine atom in direct substitution it could be very harmful in laboratory.

Complete step by step answer:
If we use fluorine gas directly it can be very explosive due to its very small size and more electrons around the fluorine nucleus.
So in laboratory we synthesis \[({C_6}{H_5}F)\] indirectly, which is known as Balz-Schiemann reaction in which we will take aniline as a substrate which will react with \[HN{O_2}\] (nitrous acid) in the presence of fluoroboric acid and gives a product diazonium salt. As the diazo group is a good leaving group so by reacting diazo-benzene with \[HB{F_4}\],this fluoroboric acid attacks the diazo group and replaces diazo with fluorine atom. The \[HB{F_4}\] gives fluoride ion as a nucleophile which attacks on diazo group. So the final product we will get as \[({C_6}{H_5}F)\].
The mechanism is shown as below.
seo images

Therefore, the correct option is option (B).
Diazotization can also occur in the presence of other acids such as sulphuric acid, hydrochloric acid.