Question

Correct reactivity order towards electrophilic addition reaction is:

• A. a > b
• B. b > a
• C. a = b
• D. can not predict

Answer 1

The correct option is B b > a

When electrophilic addition reaction takes place, carbocation forms. If electrophilic addition reaction takes place at (a), positive charge will form on doubly bonded carbon atom, but when electrophilic addition reaction takes place at (b), positive charge will form on singly bonded carbon atom. As we know electronegativity of $sp$ hybridised carbon atom is more than $s{p}^2$ hybridised carbon atom, positive charge will be unstable on $s{p}^2$ hybridised carbon atom. As the intermediate which is formed is stable in case of alkene, reactivity of alkene is more than alkyne. Hence, the correct answer is option (b).