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

Robinson Annulation

Organic Chemistry

25. Condensation Chemistry

Robinson Annulation

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Problem 36b

Textbook Question

Draw the product obtained by heating each pair of ketones in a basic solution.
b.

Verified step by step guidance

Identify the reaction type: Heating ketones in a basic solution typically leads to an aldol condensation reaction. This involves the formation of a β-hydroxyketone intermediate, which can dehydrate to form an α,β-unsaturated ketone.

Determine the enolate ion formation: In a basic solution, one of the ketones will act as a nucleophile by forming an enolate ion. This occurs when the base abstracts an α-hydrogen from the ketone, generating a resonance-stabilized enolate ion.

Perform the nucleophilic attack: The enolate ion will attack the carbonyl carbon of the second ketone, forming a new carbon-carbon bond. This step results in the formation of a β-hydroxyketone intermediate.

Account for dehydration: Under heating conditions, the β-hydroxyketone intermediate undergoes dehydration (loss of water) to form an α,β-unsaturated ketone. This step involves the elimination of a hydroxide ion and a proton, leading to the formation of a double bond between the α and β carbons.

Draw the final product: Combine the structural changes from the aldol condensation reaction to depict the α,β-unsaturated ketone product. Ensure that the double bond is correctly placed between the α and β carbons, and verify the connectivity of all atoms in the molecule.

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Key Concepts

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

Ketones

Ketones are organic compounds characterized by a carbonyl group (C=O) bonded to two carbon atoms. They are commonly represented by the general formula R2C=O, where R can be any alkyl or aryl group. Understanding the structure and reactivity of ketones is essential for predicting the products formed during chemical reactions, especially under different conditions such as heating or in the presence of a base.

Base-Catalyzed Reactions

Base-catalyzed reactions involve the use of a base to facilitate the reaction process, often by deprotonating a molecule to form a more reactive species. In the context of ketones, heating in a basic solution can lead to various reactions, including aldol condensation, where two ketones react to form a β-hydroxy ketone, which can further dehydrate to yield an α,β-unsaturated ketone. Understanding the role of the base is crucial for predicting the reaction pathway.

Aldol Condensation

Aldol condensation is a reaction between two carbonyl compounds, typically aldehydes or ketones, in the presence of a base, leading to the formation of β-hydroxy carbonyl compounds. Upon heating, these compounds can undergo dehydration to form α,β-unsaturated carbonyl compounds. This reaction is significant in organic synthesis as it allows for the formation of larger, more complex molecules from simpler precursors, highlighting the importance of understanding reaction mechanisms.

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