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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6:37 minutes

Problem 62c

Textbook Question

Predict the products of the following aldol condensations. Show the products both before and after dehydration.
(c)

Verified step by step guidance

Step 1: Identify the reactants and the type of reaction. The reactants are benzaldehyde (PhCHO) and acetone (CH3COCH3), and the reaction is an aldol condensation under basic conditions (-OH). Aldol condensation involves the formation of a β-hydroxy ketone or aldehyde followed by dehydration to form an α,β-unsaturated carbonyl compound.

Step 2: Determine the enolate formation. Under basic conditions, acetone will form an enolate ion by deprotonation of one of its α-hydrogens. The enolate ion is nucleophilic and will attack the electrophilic carbonyl carbon of benzaldehyde.

Step 3: Perform the nucleophilic addition. The enolate ion from acetone attacks the carbonyl carbon of benzaldehyde, forming a β-hydroxy ketone intermediate. This intermediate contains both a hydroxyl group (-OH) and a ketone group (-C=O) on adjacent carbons.

Step 4: Dehydration of the β-hydroxy ketone. Under the reaction conditions, the β-hydroxy ketone undergoes elimination of water (dehydration) to form an α,β-unsaturated ketone. This step involves the formation of a double bond between the α and β carbons.

Step 5: Predict the final product. After dehydration, the product will be an α,β-unsaturated ketone where the benzaldehyde-derived phenyl group (Ph) is attached to the β-carbon of the unsaturated ketone. The structure of the product can be represented as Ph-CH=CH-COCH3.

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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 at least one alpha-hydrogen. In this process, two carbonyl compounds react in the presence of a base to form a beta-hydroxy aldehyde or ketone, which can further dehydrate to yield an alpha, beta-unsaturated carbonyl compound. This reaction is crucial in organic synthesis for forming carbon-carbon bonds.

Dehydration Reaction

Dehydration in the context of aldol condensation refers to the elimination of a water molecule from the beta-hydroxy aldehyde or ketone product. This step typically occurs under heat or acidic conditions, resulting in the formation of a more stable alpha, beta-unsaturated carbonyl compound. Understanding this step is essential for predicting the final products of the aldol condensation.

Mechanism of Aldol Reaction

The mechanism of the aldol reaction involves several key steps: the formation of an enolate ion from a carbonyl compound, nucleophilic attack of the enolate on another carbonyl compound, and subsequent protonation to form the beta-hydroxy carbonyl. This understanding of the mechanism is vital for predicting the structure of the products and the stereochemistry involved in the reaction.

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