Q.Assertion: In monohaloarenes, electrophilic substitution occurs at ortho and para positions. Reason: Halogen atom is a ring deactivator.

Haloarenes DO undergo the ring's signature aromatic electrophilic substitution, but with two twists relative to plain benzene, both traceable to the halogen's dual electronic character. Rate-wise, the halogen's -I (inductive, electron-withdrawing, through the sigma framework) effect wins out overall, so halobenzenes react SLOWER than benzene itself with a given electrophile -- the halogen is a net deactivator. Orientation-wise, the halogen's lone pair simultaneously donates BY RESONANCE into the ring pi system, which specifically raises electron density at the ortho and para carbons -- so despite being an overall deactivator, the halogen is an ortho/para DIRECTOR, and o-/p- products dominate over meta. Four textbook reactions all show this same o-/p- (para-major) pattern: halogenation (chlorobenzene + Cl2/FeCl3/dark gives o- and p-dichlorobenzene), nitration (+ HNO3/con …