Organic reactions are broadly classified into different types based on how the atoms or groups in molecules change during the reaction. Here are the main types of organic reactions explained simply:
1. Substitution Reactions
One atom or group in a molecule is replaced by another.
- Example:
CH₃–Cl + OH⁻ → CH₃–OH + Cl⁻
(Chlorine is replaced by OH group) - Types:
- Nucleophilic substitution (common in haloalkanes)
- Electrophilic substitution (common in benzene)
- Radical substitution
2. Addition Reactions
Atoms or groups are added across double or triple bonds, converting them into single or double bonds.
- Example:
CH₂=CH₂ + H₂ → CH₃–CH₃
(Hydrogenation of ethene) - Types:
- Electrophilic addition (alkenes, alkynes)
- Nucleophilic addition (carbonyl compounds)
3. Elimination Reactions
The opposite of addition: atoms or groups are removed, forming a double or triple bond.
- Example:
CH₃–CH₂–Br + KOH → CH₂=CH₂ + HBr
(Bromoethane gives ethene) - Types:
- β-elimination (dehydrohalogenation)
- Dehydration (loss of water)
4. Rearrangement Reactions
The structure of the molecule changes by the shifting of atoms or bonds to form a new isomer.
- Example:
CH₃–CH₂–CH₂⁺ → CH₃–CH⁺–CH₃
(Carbocation rearrangement)
5. Oxidation–Reduction (Redox) Reactions
Involve gain or loss of electrons/oxygen/hydrogen.
- Oxidation: Addition of oxygen or removal of hydrogen.
Example: Alcohol → Aldehyde → Acid - Reduction: Addition of hydrogen or removal of oxygen.
Example: Alkene + H₂ → Alkane
6. Polymerization Reactions
Small molecules (monomers) join to form large molecules (polymers).
- Example:
nCH₂=CH₂ → (–CH₂–CH₂–)ₙ
(Ethene → Polyethene)
Summary:
The main types are:
- Substitution
- Addition
- Elimination
- Rearrangement
- Oxidation–Reduction
- Polymerization