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

Aldol Condensation

Organic Chemistry

25. Condensation Chemistry

Aldol Condensation

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4:17 minutes

Problem 75d

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.
(d)

Verified step by step guidance

Step 1: Identify the product structure. The given compound contains a conjugated system with a C=C bond adjacent to a cyano group (-CN) and an ester group (-COOEt). This suggests it was formed via a Knoevenagel condensation reaction.

Step 2: Recall the general mechanism of Knoevenagel condensation. It involves the reaction of an aldehyde or ketone with an active methylene compound (a compound with acidic hydrogens between two electron-withdrawing groups).

Step 3: Analyze the product to deduce the active methylene compound. The presence of the cyano group (-CN) and ester group (-COOEt) indicates that the active methylene compound is ethyl cyanoacetate (EtOOC-CH2-CN).

Step 4: Determine the aldehyde or ketone used in the reaction. The aromatic ring with a single substituent (the conjugated C=C bond) suggests that benzaldehyde (C6H5CHO) was the aldehyde used.

Step 5: Combine the components. The Knoevenagel condensation between benzaldehyde (C6H5CHO) and ethyl cyanoacetate (EtOOC-CH2-CN) in the presence of a secondary amine catalyst would yield the given product.

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Key Concepts

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

Knoevenagel Condensation

The Knoevenagel condensation is a reaction where an active methylene compound reacts with an aldehyde or ketone in the presence of a basic catalyst, typically a secondary amine. This reaction results in the formation of a carbon-carbon double bond (C=C) and is characterized by the elimination of a small molecule, often water. It is a key reaction in organic synthesis for forming α,β-unsaturated carbonyl compounds.

Active Methylene Compounds

Active methylene compounds are organic molecules that contain a methylene group (–CH2–) adjacent to a carbonyl group (C=O) or another electron-withdrawing group. This configuration makes the methylene hydrogen atoms particularly acidic, allowing them to be deprotonated to form a nucleophile that can attack electrophiles, such as aldehydes or ketones, in reactions like the Knoevenagel condensation.

Aldol Condensation

Aldol condensation is a fundamental reaction in organic chemistry where aldehydes or ketones with α-hydrogens undergo a reaction to form β-hydroxy carbonyl compounds, which can further dehydrate to yield α,β-unsaturated carbonyl compounds. The Knoevenagel condensation can be viewed as a specific type of aldol condensation where the reaction involves an active methylene compound, highlighting the versatility of carbonyl chemistry in forming complex molecules.

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Related Practice

Textbook Question

Show how each compound can be dissected into reagents joined by an aldol condensation, then decide whether the necessary aldol condensation is feasible.

(a)

Textbook Question

Using cyclopentanone as the reactant, show the product of

b. an aldol addition.

c. an aldol condensation.

Textbook Question

Show how each compound can be dissected into reagents joined by an aldol condensation, then decide whether the necessary aldol condensation is feasible.

(b)

Textbook Question

Show how each compound can be dissected into reagents joined by an aldol condensation, then decide whether the necessary aldol condensation is feasible.

(c)

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.

(e)

Textbook Question

(f)

Textbook Question

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

Textbook Question

Predict the products of these reaction sequences.

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