Hofmann Elimination
R3N(CH3)+ + OH− → alkene + R3N + H2O
Overview
The Hofmann elimination converts a quaternary ammonium salt to an alkene, amine, and water upon heating with base. Unlike E2 elimination, Hofmann elimination favors the less substituted alkene (anti-Zaitsev). This reaction was historically used to determine amine structures by exhaustive methylation and elimination.
Participants
| Role | Substance | Coefficient | State |
|---|---|---|---|
| Product | Water H₂O | 1 | (l) |
Everyday Example
Hofmann elimination was crucial in determining the structures of complex alkaloids like morphine and quinine before modern spectroscopy.
Industrial Importance
While largely replaced by spectroscopic methods for structure determination, Hofmann elimination is still useful in synthetic chemistry for specific alkene preparations.
Properties
- Type
- Organic
- Reversible
- No
- Energy
- Exothermic
- ΔH
- -40.0 kJ/mol
- Catalyst
- Ag₂O (for quaternary salt formation)
Related Reactions
Aldol Condensation of Acetaldehyde
Amide Formation (Acetic Acid + Ammonia)
Baeyer-Villiger Oxidation
Beckmann Rearrangement (Cyclohexanone Oxime)
Bromination of Ethylene
Buchwald-Hartwig Amination
Cannizzaro Reaction of Formaldehyde
Catalytic Hydrogenation of Ethylene
Claisen Condensation (Ethyl Acetate)
Condensation Polymerization (Nylon 6,6)
Frequently Asked Questions
What is the equation for Hofmann Elimination?
The balanced equation is: R₃N(CH₃)⁺ + OH⁻ → alkene + R₃N + H₂O.
What type of reaction is Hofmann Elimination?
Hofmann Elimination is a organic reaction.
Is Hofmann Elimination exothermic or endothermic?
Hofmann Elimination is exothermic (releases energy). The enthalpy change (ΔH) is -40.0 kJ/mol.
What conditions are needed for Hofmann Elimination?
This reaction requires a catalyst (Ag₂O (for quaternary salt formation)).