Electrophilic substitution in the Bromination of Benzene

Electrophilic substitution is a type of organic reaction in which an electrophile replaces a functional group or a hydrogen atom in a molecule. The Bromination of Benzene is an example of electrophilic substitution. The reaction takes place in the presence of iron(III) bromide (FeBr3) as a catalyst.

Mechanism of the reaction

The mechanism of the reaction involves the following steps:

1. Formation of electrophile: FeBr3 acts as a catalyst and reacts with Br2 to form an intermediate complex, FeBr4- and Br+.

FeBr3 + Br2 → FeBr4- + Br+

2. Formation of the arenium ion: The Br+ attacks the benzene ring, forming a positively charged intermediate called the arenium ion or the Wheland intermediate.

Br+ + C6H6 → C6H6Br+

3. Formation of the bromobenzene: The arenium ion is stabilized by the delocalization of electrons in the benzene ring. An electron pair from the ring moves to the carbon atom bearing the positive charge, forming a new bond with the Br+ ion.

C6H6Br+ + Br- → C6H5Br + HBr

4. Regeneration of the catalyst: The FeBr4- ion acts as a Lewis base and accepts the proton from HBr, regenerating the catalyst.

FeBr4- + HBr → FeBr3 + Br-

Overall reaction: C6H6 + Br2 → C6H5Br + HBr

Conclusion

The Bromination of Benzene is an example of electrophilic substitution because the reaction involves the replacement of a hydrogen atom on the benzene ring by an electrophilic bromine ion. The reaction is catalyzed by FeBr3, which facilitates the formation of the electrophile and the stabilization of the arenium ion intermediate.

Correct option is C because here FeBr3 , it is a lewis base . So , it will take 1 Br from the Br2 molecule and the other 1 get substituted with 1 H present on the benzene ring .