why chlorobenzene is less reactive towards nucleophilic substitution reaction towards nucleophilic reaction????
In chlorobenzene, the electron pair of chlorine atom is in conjugation with π electrons of benzene ring. Thus, chlorobenzene is a resonance hybrid of the following structures:
The contributing structures III, IV and V indicate that C-Cl bond has partial double character.As a result, the C-Cl bond in chlorobenzene is shorter and hence, stronger.Thus, cleavage of C-Cl bond in benzene becomes difficult which makes it less reactive towards nucleophilic substitution.