Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

25. Condensation Chemistry

Claisen Condensation

Organic Chemistry

25. Condensation Chemistry

Claisen Condensation

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1:56 minutes

Problem 43a

Textbook Question

Show how crossed Claisen condensations could be used to prepare the following esters.
(a)

Verified step by step guidance

Step 1: Identify the ester product and determine the two components required for the crossed Claisen condensation. The product shown contains a phenyl group (Ph) attached to a ketone and an ethyl ester group. This suggests that one reactant should be a phenyl ketone (benzophenone derivative) and the other an ethyl ester.

Step 2: Recall the mechanism of a crossed Claisen condensation. This reaction involves the nucleophilic attack of an enolate ion (formed from one reactant) on the carbonyl carbon of the other reactant. Ensure that one reactant has no alpha hydrogens to prevent self-condensation.

Step 3: Choose the appropriate reactants. For this ester, the phenyl ketone (PhCOCH(CH3)) will act as the enolate donor, and ethyl acetate (CH3COOCH2CH3) will act as the electrophile. Ethyl acetate has alpha hydrogens and can form an enolate under basic conditions.

Step 4: Outline the reaction conditions. Use a strong base, such as sodium ethoxide (NaOEt), to generate the enolate from the phenyl ketone. The enolate will then attack the carbonyl carbon of ethyl acetate, forming a new C-C bond.

Step 5: After the condensation reaction, perform an acidic workup to neutralize the reaction mixture and isolate the desired ester product. This step ensures the product is stable and free from residual base.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Claisen Condensation

Claisen condensation is a reaction between two esters or an ester and a carbonyl compound in the presence of a strong base, leading to the formation of a β-keto ester or a β-diketone. This reaction involves the nucleophilic attack of an enolate ion on the carbonyl carbon of another ester, followed by the elimination of an alcohol. Understanding this mechanism is crucial for predicting the products of crossed Claisen condensations.

Crossed Claisen Condensation

Crossed Claisen condensation refers to a variation of the Claisen reaction where two different esters or an ester and a carbonyl compound react. This approach allows for the synthesis of more complex molecules by selectively forming enolate ions from one ester while avoiding self-condensation. Mastery of this concept is essential for designing synthetic pathways to specific esters, as illustrated in the question.

Enolate Ion Formation

Enolate ions are reactive intermediates formed when a base abstracts a proton from the α-carbon of a carbonyl compound, resulting in a resonance-stabilized anion. The ability to generate enolate ions is fundamental in Claisen condensations, as they act as nucleophiles in the reaction. Recognizing how to form and utilize enolate ions is key to successfully executing crossed Claisen condensations and achieving desired ester products.

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Show how crossed Claisen condensations could be used to prepare the following esters.(a)

Key Concepts

Claisen Condensation

Crossed Claisen Condensation

Enolate Ion Formation

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Show how crossed Claisen condensations could be used to prepare the following esters.
(a)