Why do alkenes prefer to undergo electrophilic addition reaction while arenes prefer electrophilic substitution reactions? Explain.
Both Alkenes and arenes are unsaturated and electron rich. In order to give a highly stable and saturated product, Alkenes undergo addition reaction to give more stable saturated product. Under this reaction hybridization transforms from sp2 to sp3.
Arenes are stabilized by resonance with delocalization of π electrons. On addition reaction to the double bond of arene, a product is obtained which is not resonance stabilized whereas on substitution the resonance stability of arene is maintained. Thus, arenes prefer to undergo substitution reaction while alkenes prefer to undergo addition reaction.