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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7:54 minutes

Problem 65d

Textbook Question

What product is obtained when the product of a Knoevenagel condensation is heated in an aqueous acidic solution?

Verified step by step guidance

Step 1: Recognize that the reaction begins with a Knoevenagel condensation. This reaction typically involves the condensation of an aldehyde or ketone with a compound containing active methylene groups, such as diethyl malonate, in the presence of a base like NaOEt.

Step 2: The product of the Knoevenagel condensation is typically an α,β-unsaturated compound. In this case, the reaction between the aldehyde and diethyl malonate will yield a compound with a conjugated double bond system.

Step 3: When the α,β-unsaturated product is heated in an aqueous acidic solution (H₃O⁺), a hydrolysis reaction occurs. The ester groups (-COOEt) in the product are hydrolyzed to carboxylic acids (-COOH).

Step 4: After hydrolysis, decarboxylation can occur under heating conditions. Decarboxylation involves the loss of a carbon dioxide molecule (CO₂) from the carboxylic acid group, resulting in the formation of a simpler organic compound.

Step 5: The final product is typically a substituted aromatic or cyclic compound, depending on the structure of the initial reactants and the intermediate formed during the reaction. Analyze the structure of the intermediate to predict the final product.

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Key Concepts

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

Knoevenagel Condensation

Knoevenagel condensation is a reaction between an aldehyde or ketone and a compound containing an active hydrogen atom, typically a malonic ester or a β-keto ester, in the presence of a base. This reaction forms a β-unsaturated carbonyl compound. The process involves the deprotonation of the active hydrogen, followed by nucleophilic attack on the carbonyl carbon, leading to the formation of a new carbon-carbon bond.

Acidic Hydrolysis

Acidic hydrolysis refers to the reaction of a compound with water in the presence of an acid, which often catalyzes the reaction. In the context of organic compounds, this process can lead to the cleavage of bonds and the formation of new functional groups. For example, heating a product from a Knoevenagel condensation in an acidic solution can result in the hydrolysis of the β-unsaturated carbonyl compound, yielding carboxylic acids or other derivatives.

Thermal Stability of Products

The thermal stability of organic compounds refers to their ability to withstand heat without undergoing decomposition or significant structural change. In the case of products formed from Knoevenagel condensation, heating can promote further reactions, such as hydrolysis or rearrangement, especially in the presence of acid. Understanding the stability of these products is crucial for predicting the outcome of reactions when subjected to heat and acidic conditions.

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Related Practice

Textbook Question

Show how Claisen condensations could be used to make the following compounds.

(c)

Textbook Question

Show how Claisen condensations could be used to make the following compounds.

(d)

Textbook Question

Predict the products of the following Claisen condensations.

(a)

(b)

Textbook Question

There are other condensation reactions similar to the aldol and Claisen condensations:

a. The Perkin condensation is the condensation of an aromatic aldehyde and acetic anhydride. Draw the product obtained from the following Perkin condensation:

Textbook Question

There are other condensation reactions similar to the aldol and Claisen condensations:

c. The Knoevenagel condensation is the condensation of an aldehyde or a ketone that has no a-hydrogens and a compound such as diethyl malonate that has an a-carbon flanked by two electron-withdrawing groups. Draw the product obtained from the following Knoevenagel condensation:

Textbook Question

The Knoevenagel condensation is a special case of the aldol condensation in which an active methylene compound reacts with an aldehyde or ketone, in the presence of a secondary amine as a basic catalyst, to produce a new C=C. Show the starting materials that made each of these by a Knoevenagel condensation.

(a)

Textbook Question

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

(a)

Textbook Question

Propose mechanisms for the reactions shown in Problems 22-63 part (b).

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