Question

Name the compound which is most reactive towards electrophilic substitution.

Answer 1

Electrophilic substitution reaction

1. An electrophilic substitution reaction is a chemical reaction in which the functional group attached to a compound is replaced by an electrophile.
2. An electrophile is an electron-deficient species, it reacts with the compound having high electron density.
3. Electrophilic substitution reactions generally proceed via a three-step mechanism that involves the following steps.

• The generation of an electrophile
• The formation of an intermediate (carbocation)
• The removal of a proton from the intermediate

Fig: Diagram of electrophilic substitution reaction

Compounds which is most reactive towards electrophilic substitution

• Electron releasing groups increases the reactivity of a reactant towards an electrophile.
• Example: Methyl group , alkoxy group etc.
• The methyl group induces a positive inductive effect on the benzene ring which increases the electron density on the ring, so an electrophile is drawn towards it for substitution.
• The reactivity of the benzene ring increases with an increase in the electron density on it. The groups that increase the electron density on the ring increase the reactivity towards electrophilic substitution. These groups show +I or +M effect releasing electrons towards the benzene ring.

Thus, electron releasing groups increase the reactivity of a reactant towards an electrophile.