The conjugated dienes are more reactive than alkenes which in turn are more reactive than alkynes towards electrophilic addition reactions- explain.

Explanation

The reactivity of alkenes, alkynes or conjugated dienes towards electrophilic addition reaction depends on the stability of the intermediate carbocation obtained in the rate-determining step by addition of the electrophile `(E^(+))`

Out of the three carbocations (Ia, IIa and IIIa) is the most stable because it is stabilised by resonance. Again, out of (Ia) and (IIa), (IIa) is less stable because the positive charge in it is placed on a more electronegative `sp^(2)`-hybridised carbon atom. Thus, the stabilities of these carbocations follow the order: `IIIa gt Ia gt IIa`. Therefore, the order of reactivity of these compounds is: conjugated diene `gt` alkene `gt` alkyne