Question

What is the right order of relative activity in an electrophilic substitution reaction? Briefly explain your answer

A.

OH CH2CH3

B.

C.

D.

Answer 1

The order of electrophilic substitution reaction depends upon the ease by which an electrophile attacks and this depends completely on the substituent attached to the benzene ring.

Thus, the substituents that activates the ring (by giving electrons) are the one with fastest electrophilic substitution reaction while those substituents that deactivates the ring (by pulling the electron density towards themselves) show slowest electrophilic substitution reaction.

Out of the given four orders, the correct order of relative activity in electrophilic substitution reaction is that of OPTION- 'C'

This is because:

• OH group in phenol is an activating group as it gives electron by resonance (+R) effect.
• Ethyl group in ethyl benzene is also activating as it gives electron by hyperconjugation or inductive effect (+I)
• Halogens are deactivating groups as they deactivates the ring by (-I) effect, unlike benzene which has no substituent attached to it therefore, benzene comes before chlorobenzene in the reactivity order.