Answer
🧪 Claisen Condensation Reaction – Full Mechanism Explained
🔹 Step 1: Introduction
This transformation is a classic Claisen condensation, which is a C–C bond-forming reaction between two esters or an ester and a ketone. A strong base, such as sodium ethoxide (NaOEt), is used to abstract an α-proton and generate an enolate ion.
Final Product: β-Keto Ester
Type: Mixed Claisen Condensation (Ketone + Ester)
Type: Mixed Claisen Condensation (Ketone + Ester)
🔬 Step-by-Step Reaction Mechanism
Step 1 – Enolate Formation:
Sodium ethoxide abstracts an α-hydrogen from the ketone, forming a resonance-stabilized enolate ion.
Sodium ethoxide abstracts an α-hydrogen from the ketone, forming a resonance-stabilized enolate ion.
Step 2 – Nucleophilic Attack:
The enolate ion attacks the carbonyl carbon of the ester, producing a tetrahedral intermediate.
The enolate ion attacks the carbonyl carbon of the ester, producing a tetrahedral intermediate.
Step 3 – Elimination of Ethoxide:
The intermediate collapses, eliminating ethoxide and forming a new C=O bond.
The intermediate collapses, eliminating ethoxide and forming a new C=O bond.
Step 4 – Reprotonation (Optional):
The β-keto ester may be reprotonated under neutral or acidic conditions to stabilize the product.
The β-keto ester may be reprotonated under neutral or acidic conditions to stabilize the product.
📘 Summary Table
| Step | Description |
|---|---|
| Enolate Formation | Base deprotonates α-carbon of ketone |
| Nucleophilic Attack | Enolate attacks ester carbonyl carbon |
| Elimination | Loss of ethoxide and reformation of carbonyl group |
| Protonation | Formation of stable β-keto ester |
✅ Final Product & Confirmation
The final product is a β-keto ester, formed via a condensation reaction between a ketone-derived enolate and an ester. This validates the reaction as a mixed Claisen condensation.
🧠Conclusion
Claisen condensation is one of the most important carbon–carbon bond-forming reactions in organic chemistry. It is crucial for constructing β-keto esters, which are useful intermediates in complex molecule synthesis, including pharmaceuticals and natural products.