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

Intramolecular Aldol Condensation

Organic Chemistry

25. Condensation Chemistry

Intramolecular Aldol Condensation

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Problem 40a,b

Textbook Question

Some (but not all) of the following keto esters can be formed by Dieckmann condensations. Determine which ones are possible, and draw the starting diesters.
(a)
(b)

Verified step by step guidance

Step 1: Understand the Dieckmann condensation reaction. The Dieckmann condensation is an intramolecular Claisen condensation where a diester reacts with a base to form a cyclic β-keto ester. This reaction typically forms 5- or 6-membered rings due to favorable ring strain considerations.

Step 2: Analyze the given keto esters. For each keto ester, determine whether it can form a 5- or 6-membered ring upon cyclization. If the structure of the keto ester suggests a ring size outside this range, it is unlikely to form via a Dieckmann condensation.

Step 3: Identify the starting diester for each keto ester. To do this, reverse the Dieckmann condensation mechanism. Break the β-keto ester at the bond between the α-carbon and the carbonyl carbon of the ester group. Add an ester group to the α-carbon to reconstruct the starting diester.

Step 4: Verify the feasibility of the reaction. Check whether the starting diester can undergo an intramolecular reaction to form the desired cyclic β-keto ester. Ensure that the reaction conditions (e.g., base and solvent) would favor the formation of the product.

Step 5: Draw the starting diesters for the keto esters that can be formed via Dieckmann condensation. For those that cannot be formed, provide a brief explanation of why the reaction is not feasible (e.g., ring strain or improper positioning of ester groups).

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Key Concepts

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

Dieckmann Condensation

Dieckmann condensation is a specific type of intramolecular aldol reaction that occurs between two ester groups in the presence of a strong base. This reaction typically leads to the formation of a β-keto ester. Understanding the mechanism involves recognizing how the base deprotonates the ester, allowing for nucleophilic attack on the carbonyl carbon of another ester group, ultimately forming a cyclic product.

Keto Esters

Keto esters are organic compounds that contain both a ketone and an ester functional group. They are characterized by the presence of a carbonyl group (C=O) adjacent to an ester group (RCOOR'). The formation of keto esters through Dieckmann condensation is significant in organic synthesis, as they can serve as intermediates for further reactions, including cyclization and functional group transformations.

Starting Diesters

Starting diesters are the initial compounds required for the Dieckmann condensation reaction. They typically consist of two ester groups separated by a carbon chain. The structure and length of this chain are crucial, as they determine the feasibility of the intramolecular reaction and the formation of a cyclic product. Identifying the correct starting diesters is essential for predicting which keto esters can be synthesized through this method.

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