Question

Why alkenes more reactive than alkynes although alkynes are more unsaturated than alkenes?

Answer 1

alkynes are more reactive than alkenes

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.


HOPE MY ANSWER WILL HELP U.

REGARD
YUSUF@