What is the mechanism of electrophilic substitution and how does it relate to aromatic compounds?

Electrophilic substitution is a reaction mechanism where an electrophile replaces a hydrogen atom in an aromatic compound.

Aromatic compounds are organic compounds that contain a benzene ring or a related ring structure. They are characterised by their stability and unique properties, such as their ability to undergo electrophilic substitution reactions. In these reactions, an electrophile (a species that is attracted to electrons) attacks the aromatic ring, replacing one of the hydrogen atoms. This results in the formation of a new compound with a different functional group attached to the ring.

The mechanism of electrophilic substitution involves three main steps: activation, attack, and deactivation. In the activation step, the electrophile is attracted to the electron-rich pi bonds in the aromatic ring. This is followed by the attack step, where the electrophile attacks the ring, forming a carbocation intermediate. Finally, in the deactivation step, the intermediate is stabilised by the loss of a proton, resulting in the formation of the substituted aromatic compound.

Electrophilic substitution is an important mechanism in organic chemistry, particularly in the synthesis of pharmaceuticals, dyes, and other organic compounds. Understanding the mechanism of electrophilic substitution is crucial for A-Level Biology students who wish to pursue a career in chemistry or related fields.