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

Crossed Aldol Condensation

Organic Chemistry

25. Condensation Chemistry

Crossed Aldol Condensation

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5:17 minutes

Problem 69d

Textbook Question

Predict the products of the following reactions.
(d)

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Step 1: Identify the reactants and reaction conditions. The reactants are formaldehyde (HCHO) and cyclohexanone (C6H10O), and the reaction is carried out in the presence of a hydroxide ion (OH⁻) and heat (Δ). This suggests an aldol condensation reaction.

Step 2: Determine the enolate formation. Cyclohexanone has an alpha hydrogen, which can be deprotonated by the hydroxide ion to form an enolate ion. The enolate ion is nucleophilic and will attack the electrophilic carbonyl carbon of formaldehyde.

Step 3: Describe the nucleophilic addition step. The enolate ion attacks the carbonyl carbon of formaldehyde, forming a beta-hydroxy ketone intermediate. This intermediate is characteristic of the aldol addition reaction.

Step 4: Explain the dehydration step. Under the influence of heat (Δ), the beta-hydroxy ketone undergoes elimination of water (H₂O) to form an α,β-unsaturated ketone. This step is known as aldol condensation.

Step 5: Predict the final product. The final product will be an α,β-unsaturated ketone where the double bond is conjugated with the carbonyl group. The structure will consist of a cyclohexane ring with a double bond adjacent to the ketone group, and the formaldehyde-derived carbon will be part of the conjugated system.

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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 compound, followed by dehydration to yield an α,β-unsaturated carbonyl compound. Understanding this mechanism is crucial for predicting the products of the reaction shown.

Enolate Ion Formation

Enolate ions are formed when a carbonyl compound, such as an aldehyde or ketone, is deprotonated at the alpha position. This ion acts as a nucleophile in aldol reactions, attacking the carbonyl carbon of another molecule. Recognizing how enolate ions are generated and their role in the reaction mechanism is essential for predicting the products of the aldol condensation.

Dehydration Step

The dehydration step in aldol condensation involves the elimination of a water molecule from the β-hydroxy carbonyl compound, resulting in the formation of an α,β-unsaturated carbonyl compound. This step is driven by the stability of the resulting double bond and is often facilitated by heat. Understanding this step is important for accurately predicting the final products of the reaction.

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Related Practice

Textbook Question

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

(c)

(d)

Multiple Choice

Give the structure of the aldehydes or ketones used to create the product prepared by a crossed aldol condensation reaction.

Multiple Choice

Give the structure of the aldehydes or ketones used to create the product prepared by a crossed aldol reaction.

Multiple Choice

What product can be isolated from the following aldol condensation reaction?

Textbook Question

Predict the major products of the following base-catalyzed aldol condensations with dehydration.

(b) 2,2-dimethylpropanal + acetophenone

Textbook Question

Predict the major products of the following base-catalyzed aldol condensations with dehydration.

(a) benzophenone (PhCOPh) + propionaldehyde

Textbook Question

Propose mechanisms for the following base-catalyzed condensations, with dehydration.

(b) benzaldehyde with propionaldehyde

Textbook Question

Propose mechanisms for the following base-catalyzed condensations, with dehydration.

(a) 2,2-dimethylpropanal with acetaldehyde

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Predict the products of the following reactions.(d)

Key Concepts

Aldol Condensation

Enolate Ion Formation

Dehydration Step

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Predict the products of the following reactions.
(d)