Explain bromination of benzene requires `FeBr_3` as catalyst, while bromination of anisole `(C_6H_5OCH_3)` does not require any catalyst.

Explanation

Since benzene molecule is not so reactive, for bromination it requires more reactive bromine cation `(Boverset(oplus)(r))` or the complex `Br - overset(oplus)(B)r - overset(Θ)(F)eBr_(3)` as the electrophile. Due to the presence of electron-donating `(+R)` methoxy `(-OCH_(3))` group, the anisole ring becomes much more reactive towards electrophillic substitution reaction. When the non-polar bromine molecule comes in contact with the anisole ring, it becomes partially polarised `(overset(delta+)(Br) - overset(delta-)(Br))` and its positive end (weak electrophile) undergoes easy attack by anisole. Therefore, due to greater reactivity of anisole its bromination requires no catalyst.