Disubstituion

Disubstitution is a term used in chemistry to describe a reaction where two substituents are added to a molecule, typically a benzene ring. This is distinct from monosubstitution where only one substituent is introduced. The position of the second substituent relative to the first is crucial and is governed by the directing effects of the initial substituent.

Electron-donating groups, such as alkyl or alkoxy groups, are ortho, para directors. This means they activate the ortho and para positions on the ring, making them more susceptible to electrophilic attack by the incoming substituent. Electron-withdrawing groups, such as nitro or carbonyl groups, are meta directors. They deactivate the ortho and para positions and direct the incoming substituent to the meta position.

The order of addition can also influence the outcome. If a strongly activating group is present, a second substituent will likely enter ortho or para to it. If a deactivating group is present, the directing effect will be meta. In some cases, steric hindrance can also play a role, favoring substitution at less crowded positions. Understanding disubstitution is fundamental to predicting the products of electrophilic aromatic substitution reactions and is important in the synthesis of various organic compounds.