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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4:56 minutes

Problem 63c

Textbook Question

Predict the products of the following Claisen condensations.
(c)

Verified step by step guidance

Step 1: Recognize that this is a Dieckmann condensation, which is an intramolecular Claisen condensation. It involves the reaction of a diester with a base to form a cyclic β-keto ester.

Step 2: Identify the two ester groups in the molecule. The molecule contains two ester functionalities: one at the end of the chain and another in the middle. The reaction will proceed by forming a cyclic structure.

Step 3: Determine the nucleophilic site. The base (methoxide ion, CH₃O⁻) will deprotonate the α-hydrogen of one of the ester groups, creating an enolate ion. This enolate will act as a nucleophile.

Step 4: Predict the intramolecular attack. The enolate ion will attack the carbonyl carbon of the other ester group, leading to the formation of a new C-C bond and a cyclic intermediate.

Step 5: Finalize the product structure. After the intramolecular attack, the intermediate undergoes protonation and elimination of methoxide (CH₃O⁻), resulting in a cyclic β-keto ester as the final product. The ring size will depend on the number of carbons between the two ester groups.

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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, typically sodium ethoxide. This reaction results in the formation of a β-keto ester or a β-diketone. Understanding this mechanism is crucial for predicting the products, as it involves nucleophilic attack and subsequent elimination of an alcohol.

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a fundamental reaction in organic chemistry where a nucleophile attacks an acyl compound, leading to the substitution of a leaving group. In the context of Claisen condensation, the enolate ion formed from one ester acts as the nucleophile, attacking the carbonyl carbon of another ester. This concept is essential for understanding how the products are formed during the reaction.

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. In Claisen condensation, the formation of the enolate ion is a critical step, as it serves as the nucleophile that initiates the reaction. Recognizing how enolate ions are generated and their role in the reaction mechanism is vital for predicting the final products.

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Related Practice

Textbook Question

Predict the major products of the following crossed Claisen condensations.

(b)

Textbook Question

Show what esters would undergo Claisen condensation to give the following β-keto esters.

(c)

Textbook Question

Propose mechanisms for the following reactions.

(b)

Textbook Question

Propose a mechanism for the self-condensation of methyl 3-phenylpropionate promoted by sodium methoxide.

Textbook Question

Ethoxide is used as the base in the condensation of ethyl acetate to avoid some unwanted side reactions. Show what side reactions would occur if the following bases were used.

(a) sodium methoxide

(b) sodium hydroxide

Textbook Question

Esters with only one α hydrogen generally give poor yields in the Claisen condensation. Propose a mechanism for the Claisen condensation of ethyl isobutyrate, and explain why a poor yield is obtained.

Textbook Question

Predict the products of self-condensation of the following esters.

(a) methyl propanoate + NaOCH₃

(b) ethyl phenylacetate + NaOCH2CH₃

Textbook Question

Predict the products from crossed Claisen condensation of the following pairs of esters. Indicate which combinations are poor choices for crossed Claisen condensations.

(a)

(b)

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Predict the products of the following Claisen condensations.(c)

Key Concepts

Claisen Condensation

Nucleophilic Acyl Substitution

Enolate Ion Formation

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Predict the products of the following Claisen condensations.
(c)