Question

Why haloarenes are Less reactive than halo alkanes?

Answer 1

1. The low reactivity of aryl halides is due to resonance effect and sp² hybrid state of carbon to which halogen atom is attached.
2. In aryl halides, one of the lone pairs of electrons on halogen atom is in conjugation with ρ-electrons of the ring. Due to resonance. the C-X bond acquires partial double bond character. Thus, the C-X bond in haloarenes is stronger and shorter than haloalkanes. Hence. it is difficult to break C-X bond in haloarenes. (e.g. C-Cl bond length in chlorobenzene is 169 pm as compared to C-Cl bond length in alkyl chloride which is 178 pm).