Thus, C—Cl bond length in haloalkane is
177pm while in haloarene is 169 pm Since it is difficult to
break a shorter bond than a longer bond, therefore, haloarenes
are less reactive than haloalkanes towards nucleophilic
substitution reaction (iii) Instability of phenyl cation: In case of haloarenes, the phenyl
cation formed as a result of self-ionisation will not be stabilised
by resonance and therefore, SN1 mechanism is ruled out (iv) Because of the possible repulsion, it is less likely for the electron
rich nucleophile to approach electron rich arenes