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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Problem 65a

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:

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Identify the reactants in the Perkin condensation: an aromatic aldehyde (e.g., benzaldehyde) and acetic anhydride. The reaction typically occurs in the presence of a base, such as sodium acetate, which facilitates the reaction.

Understand the mechanism: The base deprotonates the methyl group of acetic anhydride, forming an enolate ion. This enolate ion acts as a nucleophile in the reaction.

The enolate ion attacks the carbonyl carbon of the aromatic aldehyde, forming a β-hydroxy intermediate. This step is analogous to the aldol addition step in aldol condensation.

The β-hydroxy intermediate undergoes dehydration (loss of water) to form an α,β-unsaturated carbonyl compound. This step is driven by the formation of a conjugated system, which is thermodynamically stable.

Draw the final product: The product will be an α,β-unsaturated carbonyl compound where the aromatic ring is conjugated with the double bond and the carbonyl group. Ensure the structure reflects the correct connectivity and stereochemistry, if applicable.

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Key Concepts

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

Perkin Condensation

The Perkin condensation is a reaction that involves the condensation of an aromatic aldehyde with an anhydride, typically acetic anhydride, in the presence of a base. This reaction results in the formation of α,β-unsaturated carboxylic acids. Understanding this reaction is crucial for predicting the structure of the product formed from the specific reactants provided in the question.

Aromatic Aldehydes

Aromatic aldehydes are organic compounds that contain a carbonyl group (C=O) bonded to a carbon atom of an aromatic ring. They play a significant role in various organic reactions, including the Perkin condensation. Recognizing the structure and reactivity of aromatic aldehydes is essential for determining the outcome of the condensation reaction.

Acetic Anhydride

Acetic anhydride is a reactive acylating agent commonly used in organic synthesis, particularly in condensation reactions. It can donate an acetyl group (CH3CO-) to other molecules, facilitating the formation of new carbon-carbon bonds. Familiarity with acetic anhydride's properties and its role in the Perkin condensation is vital for understanding the mechanism and predicting the product.

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Related Practice

Textbook Question

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

(b)

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

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

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)

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