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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3:01 minutes

Problem 32c

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)

Verified step by step guidance

Step 1: Identify the product of the aldol condensation. The given compound contains a β-hydroxy ketone structure that has undergone dehydration to form an α,β-unsaturated ketone. This indicates it is the result of an aldol condensation followed by elimination of water.

Step 2: Break the compound into two potential reagents. In an aldol condensation, one reagent acts as the enolate ion (nucleophile) and the other as the carbonyl compound (electrophile). Here, the compound can be dissected into benzaldehyde (PhCHO) and acetone (CH3COCH3).

Step 3: Analyze the feasibility of forming the enolate. Acetone can form an enolate ion under basic conditions because it has acidic α-hydrogens adjacent to the carbonyl group. This enolate can attack the electrophilic carbonyl carbon of benzaldehyde.

Step 4: Consider the aldol addition step. The enolate ion of acetone will attack the carbonyl carbon of benzaldehyde, forming a β-hydroxy ketone intermediate. This intermediate is stable under basic conditions.

Step 5: Evaluate the dehydration step. Under heating or continued basic conditions, the β-hydroxy ketone intermediate undergoes elimination of water to form the α,β-unsaturated ketone product shown in the image. This dehydration step is feasible and commonly occurs in aldol condensations.

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Key Concepts

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

Aldol Condensation

Aldol condensation is a reaction between aldehydes or ketones that contain alpha-hydrogens, leading to the formation of β-hydroxy aldehydes or ketones. This reaction involves the nucleophilic addition of an enolate ion to a carbonyl carbon, followed by dehydration to form an α,β-unsaturated carbonyl compound. Understanding this mechanism is crucial for dissecting compounds into their respective reagents.

Enolate Ion Formation

Enolate ions are formed when a base abstracts an alpha-hydrogen from a carbonyl compound, resulting in a resonance-stabilized anion. This ion acts as a nucleophile in aldol reactions, allowing it to attack another carbonyl compound. Recognizing how to generate enolate ions from the given compounds is essential for determining the feasibility of the aldol condensation.

Feasibility of Aldol Condensation

The feasibility of an aldol condensation depends on the stability of the resulting products and the reaction conditions. Factors such as steric hindrance, electronic effects, and the presence of suitable bases or acids influence whether the reaction will proceed. Evaluating these factors helps in deciding if the aldol condensation can occur with the given compounds.

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Related Practice

Textbook Question

Propose a mechanism for the dehydration of diacetone alcohol to mesityl oxide

(a) in acid.

(b) in base.

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

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)

Textbook Question

(e)

Textbook Question

(f)

Textbook Question

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

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