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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6:29 minutes

Problem 32

Textbook Question

Write the mechanism for the reaction of a 1,7-diester with an alkoxide ion to form a cyclic b-keto ester.

Verified step by step guidance

Identify the starting material: The 1,7-diester contains two ester groups separated by six carbon atoms. This structure allows for the formation of a six-membered ring during the reaction.

Recognize the role of the alkoxide ion: The alkoxide ion acts as a base, abstracting a proton from the α-carbon (the carbon adjacent to one of the ester groups) to generate an enolate ion. This enolate is stabilized by resonance between the α-carbon and the carbonyl group.

Illustrate the nucleophilic attack: The enolate ion, acting as a nucleophile, attacks the carbonyl carbon of the second ester group within the same molecule. This intramolecular reaction forms a new carbon-carbon bond, initiating the formation of a six-membered ring.

Depict the tetrahedral intermediate: The nucleophilic attack results in a tetrahedral intermediate at the carbonyl carbon of the second ester group. This intermediate is unstable and will collapse, leading to the elimination of the alkoxide group (from the second ester).

Show the final product: The elimination of the alkoxide group results in the formation of a cyclic β-keto ester. The six-membered ring structure is stabilized by the conjugation between the ketone and ester groups.

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Key Concepts

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

Diester Reactivity

Diesters are compounds containing two ester functional groups. In the context of organic reactions, they can undergo nucleophilic attack due to the electrophilic nature of the carbonyl carbon. Understanding the reactivity of diesters is crucial for predicting how they will interact with nucleophiles, such as alkoxide ions, in a reaction mechanism.

Nucleophilic Substitution Mechanism

Nucleophilic substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophile, resulting in the replacement of a leaving group. In this case, the alkoxide ion acts as the nucleophile, attacking the carbonyl carbon of the diester, leading to the formation of a cyclic structure. Familiarity with this mechanism is essential for understanding how cyclic b-keto esters are formed.

Cyclic b-Keto Esters

Cyclic b-keto esters are cyclic compounds that contain both a ketone and an ester functional group. Their formation often involves intramolecular reactions, where a nucleophile attacks a carbonyl within the same molecule. Recognizing the structure and properties of cyclic b-keto esters is important for predicting their stability and reactivity in further chemical transformations.

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Related Practice

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)

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.

(c)

(d)

Textbook Question

Show how you would use an aldol, Claisen, or another type of condensation to make each compound.

(d)

Textbook Question

Draw the products of the following reactions:

d. diethyl 1,2-benzenedicarboxylate + sodium ethoxide: (1) slow addition of ethyl acetate; (2) HCl

Textbook Question

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

(a)

Textbook Question