sir i have ques: among chlorobenzene and meta-nitrochlorobenzene which one will undergo nucleophilic subst. reaction more easily? Or will both undergo the reaction with same ease?

The nitro group exerts two electron withdrawing effects, -M and -I. So it wil make the ring electron deficient and willl activate the ring carbons very strongly to receive a nucleophile while the chloro has -I effect only.Thus chlorobenzene will undergo nucleophilic substitution slower than nitrobenzene.