¶ Aromatic substitution
¶ Electrophilic Substitution
Aromatic compounds do not want to participate in addition reactions as doing so will break the conjugation and take away their stability
- However, it is able to undergo reactions such as substitution, but will aim to restore its aromaticity
¶ Electrophilic aromatic substitution
It is the main mode of reactivity of aromatic compounds
The identity of the electrophile is specific to each type of reaction the aromatic compound undergoes
(In some cases, we even have to generate the electrophiles)
¶ Mechanism
When aromatic compounds react with electrophiles, they generally do so through the SEAr mechanism
Carbocation intermediate is stabilized through resonance
- It is important to notice that even though the positive charge is delocalised, the intermediate is not aromatic due to the fact that the carbon bonded to the electrophile is sp3 hybridised (and the ring is not fully planar)
The reaction has a two-step mechanism and the first step is rate determining step
¶ Ipso-Substitution
The electrophiles are able to attack substituted carbons rather than just hydrogen-bearing carbons