- A substitution reaction is an organic reaction in which one atom or group in a molecule is replaced by another atom or group.
- Think of it as swapping one part of a molecule for another.
General Example
- If molecule A–B reacts with C, and B is replaced by C, the reaction is:
A–B + C → A–C + B
Types of Substitution Reactions
- Nucleophilic Substitution
- A nucleophile (electron-rich species) replaces another group.
- Example: Chloromethane + OH⁻ → Methanol + Cl⁻
- Electrophilic Substitution
- An electrophile (electron-seeking species) replaces a hydrogen atom in an aromatic compound.
- Example: Benzene + Br₂ → Bromobenzene + HBr
Key Points
- Substitution reactions are common in organic chemistry.
- They are important for making drugs, dyes, and polymers.
In short:
A substitution reaction is when one atom or group in a molecule is replaced by another atom or group.