Answer
🔬 Acetoacetic Ester Synthesis
🧪 Reaction Overview
This reaction is used to synthesize mono-substituted ketones from ethyl acetoacetate through enolate alkylation, ester hydrolysis, and decarboxylation.
CH₃COCH₂COOC₂H₅ → CH₃COCH(PhCH₂)COOC₂H₅ → CH₃COCH(PhCH₂)COOH → CH₃COCH₂Ph
🔬 Mechanism Steps
Step 1: Enolate Formation
Reagent: Sodium ethoxide (NaOEt)
NaOEt deprotonates the acidic α-hydrogen to form an enolate ion.
CH₃COCH₂COOC₂H₅ + NaOEt → CH₃COCH⁻COOC₂H₅
Step 2: Alkylation
Reagent: Benzyl bromide (PhCH₂Br)
The enolate undergoes an SN2 reaction with the alkyl halide to form a substituted β-keto ester.
CH₃COCH⁻COOC₂H₅ + PhCH₂Br → CH₃COCH(PhCH₂)COOC₂H₅
Step 3: Ester Hydrolysis
Condition: Dilute acid (H₃O⁺)
The ester is hydrolyzed to the corresponding β-keto acid.
CH₃COCH(PhCH₂)COOC₂H₅ + H₃O⁺ → CH₃COCH(PhCH₂)COOH
Step 4: Decarboxylation
Condition: Heat
The β-keto acid undergoes decarboxylation to form the final ketone product.
CH₃COCH(PhCH₂)COOH → CH₃COCH₂Ph + CO₂
✅ Final Product
Benzyl methyl ketone (PhCH₂COCH₃)
🔧 Reagent Summary
| Step | Transformation | Reagent/Condition |
|---|---|---|
| 1 | Enolate formation | NaOEt |
| 2 | Alkylation | PhCH₂Br |
| 3 | Hydrolysis | H₃O⁺ (acidic workup) |
| 4 | Decarboxylation | Heat |
🧠 Key Concepts:
- Ethyl acetoacetate acts as a nucleophile via its enolate form.
- Alkylation introduces the desired side chain at the α-position.
- Hydrolysis and decarboxylation yield the substituted ketone.