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Claisen condensation between

Mechanism of the. Claisen condensation between. Ethyl Benzoate and Ethyl Propanoate. Rainer Ludwig Claisen (1851-1930) Developed the “Claisen Condensation” in 1887. What are the building blocks?. ETHYL PROPANOATE. ETHYL BENZOATE . CARBON. ETHOXIDE ION. HYDROGEN. sp 2 orbitals. O.

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Claisen condensation between

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  1. Mechanism of the Claisen condensation between Ethyl Benzoate and Ethyl Propanoate Rainer Ludwig Claisen (1851-1930) Developed the “Claisen Condensation” in 1887

  2. What are the building blocks? ETHYL PROPANOATE ETHYL BENZOATE CARBON ETHOXIDE ION HYDROGEN

  3. sp2 orbitals O O p orbitalsπ bond α hydrogens C C C O C sp3 orbitals C

  4. High Electronegativity of Oxygen FORCE & ENERGY Sites for nucleophilic attacks O C C α hydrogens

  5. FORCE & ENERGY Resonance Energy“Stabilization energy”

  6. FORCE & ENERGY O|| Formation of the enolate - Et -O - C - CH – CH3 Condensationwith ethyl benzoate to form β-keto ester Loss of 2nd alpha hydrogen on β-keto ester Ethyl propanoate O|| Et -O - C - CH2 – CH3

  7. MATHEMATICS pKa of alpha hydrogens ≈ 24 or Ka≈ 10-24 0.06 0.06 0.14 0.04 Ethyl Propanoate

  8. sp3 orbitals sp2 orbitals 109.5o 120o 90o 180o p orbitals sp orbitals MATHEMATICS Bond Angles

  9. + Overview of the Claisen Condensation Reaction 3. The enolate of ethyl propanoate is a strong nucleophile that attacks the partially positive carbon of the carbonyl group on ethyl benzoate. 2. The enolate of ethyl propanoate is formed. 1. Ethoxide ion acting as a strong base deprotonates ethyl propanoate. 6. The driving force for this reaction is the transfer of the second alpha hydrogen to the ethoxide ion. This is exothermic. 4. The alpha substitution makes this a carbonyl condensation reaction. Ethyl Propanoate 5. A β-keto ester is formed. Ethoxide ion Ethyl Benzoate

  10. + Deprotonation of Ethyl Propanoate The enolate ion is a strong nucleophile and will attack the partially positive carbon of a carbonyl group. Resonance Ethyl Benzoate Enolate of Ethyl Propanoate

  11. Self condensation of ethyl propanoate

  12. Mechanism of the Claisen condensation between Ethyl Benzoate and Ethyl Propanoate Rainer Ludwig Claisen (1851-1930) Developed the “Claisen Condensation” in 1887

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