Substitution

Substitution is a concept in chemistry where one atom, ion, or functional group in a chemical compound is replaced by another. This process can occur in various types of reactions, including nucleophilic substitution, electrophilic substitution, and free radical substitution.

Types of Substitution Reactions

Nucleophilic Substitution

In a nucleophilic substitution reaction, a nucleophile, an atom or molecule that donates an electron pair, replaces a group in a molecule. There are two main types of nucleophilic substitution reactions: SN1 and SN2.

SN1 Reaction

In an SN1 reaction, the leaving group first departs, forming a carbocation, which is then attacked by the nucleophile.

SN2 Reaction

In an SN2 reaction, the nucleophile simultaneously attacks the substrate and displaces the leaving group.

Electrophilic Substitution

In an electrophilic substitution reaction, an electrophile, an atom or molecule that accepts an electron pair, replaces a group in a molecule. This type of reaction is common in aromatic compounds, such as benzene.

Free Radical Substitution

In a free radical substitution reaction, a free radical replaces a group in a molecule. This type of reaction is common in alkanes and alkenes.

See Also

• Addition reaction
• Elimination reaction
• Rearrangement reaction