Final answer:
Haloarenes react more slowly with electrophiles compared to benzene due to the deactivating effect of the halogen substituents, which withdraw electron density from the aromatic ring, making it less reactive. the correct answer to the multiple-choice question posed is (c) Halogens in haloarenes are deactivating.
Step-by-step explanation:
Electrophilic substitution reactions in haloarenes occur more slowly and under more drastic conditions compared to benzene due to the nature of the halogen substituents. Halogens are known to be deactivating groups when attached to an aromatic ring. This means that they withdraw electron density from the ring via their inductive effect, making the ring less reactive towards electrophiles.
Since benzene rings are electron-rich due to delocalized electrons, they are considered nucleophiles, although their nucleophilic character is relatively weak compared to alkenes. The weak character is attributed to the fact that using these delocalized electrons for bonding would result in the loss of aromatic stabilization. Hence, stronger electrophiles are necessary to react with benzene. These strong electrophiles are typically generated in situ, such as from reactions between halogens and Lewis acids like AlX3 or FeX3.
Unlike alkenes that can interact with partial positive (A-B) electrophiles due to their loosely bound π electrons, the aromatic rings require cationic electrophiles because of the energy cost associated with disrupting aromatic stabilization. This cost is significantly higher in aromaatic systems compared to simple alkenes.