Question

why are alkenes more reactive than alkynes

Answer 1

The triple bond of alkynes,because of its high electron density are easily attacked by electrophile ,but less reactive than alkenes due to the compact C- C electron with electrophilic addition due to unsymmetrical alkenes, the markovnikov role is followed adding the electrophile to the less substituted carbon.

Answer 2

Alkenes are more reactive than alkynes. In order to understand this, we need to first realize that the pi bonded electons in akenes and alkyes are inherently nucleophilic and react with electrophiles to form a carbocation. Carbocations are stabilized by hyperconjugation and, the more conjugation in the system, the more stability. That said, tertiary are most stable (followed by secondary, etc). Now, when alkynes react with electrophiles, a vinylic carbocation will be formed (positive charge residing on an sp hybridized carbon atom). These vinylic carbocations are inherently less stable than those previously described (in which the positive charge is on an sp3 hybridized carbon atom). The geometry of the electron repulsion doesn't allow for hyperconjugation. Some chemistry textbooks show a free energy diagram to demonstrate this in which the delta G double-daggers is higher for the vinylic cation than the alkyl cation.




I think it helps you a lot thank u very much