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1、Claisen condensation between,Ethyl Benzoate and Ethyl Propanoate,Mechanism of the,Rainer Ludwig Claisen (1851-1930) Developed the “Claisen Condensation” in 1887,ETHYL PROPANOATE,What are the building blocks?,ETHYL BENZOATE,ETHOXIDE ION,CARBON,HYDROGEN,sp2 orbitals,p orbitals bond,sp3 orbitals, hydro
2、gens,O,C,O,O,C,C,C,C, hydrogens,O,C,C,FORCE & ENERGY,Sites for nucleophilic attacks,High Electronegativity of Oxygen,Resonance Energy “Stabilization energy”,FORCE & ENERGY,FORCE & ENERGY,Ethyl propanoate,Formation of the enolate,Condensation with ethyl benzoate to form -keto ester,Et -O - C - CH2 CH
3、3,O |,Loss of 2nd alpha hydrogen on -keto ester,Et -O - C - CH CH3,O |,-,MATHEMATICS,Ethyl Propanoate,0.04,0.14,0.06,0.06,pKa of alpha hydrogens 24 or Ka 10-24,MATHEMATICS,Bond Angles,Overview of the Claisen Condensation Reaction,Ethyl Propanoate,Ethoxide ion,Ethyl Benzoate,1. Ethoxide ion acting as
4、 a strong base deprotonates ethyl propanoate.,2. The enolate of ethyl propanoate is formed.,3. The enolate of ethyl propanoate is a strong nucleophile that attacks the partially positive carbon of the carbonyl group on ethyl benzoate.,4. The alpha substitution makes this a carbonyl condensation reac
5、tion.,5. A -keto ester is formed.,6. The driving force for this reaction is the transfer of the second alpha hydrogen to the ethoxide ion. This is exothermic.,Deprotonation of Ethyl Propanoate,Resonance,The enolate ion is a strong nucleophile and will attack the partially positive carbon of a carbonyl group.,Ethyl Propanoate,Ethyl Benzoate,Enolate of,Self condensation of ethyl propanoate,Claisen condensation between,Ethyl Benzoate and Ethyl Propanoate,Mechanism of the,Rainer Ludwig Claisen (1851-1930) Developed the “Claisen Condensation” in 1887,
