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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3:18 minutes

Problem 76a,b,c

Textbook Question

A student tried to prepare the following compounds using aldol condensations. Which of these compounds was she successful in synthesizing? Explain why the other syntheses were not successful.

Verified step by step guidance

Step 1: Understand the aldol condensation reaction. Aldol condensation involves the reaction of an enolate ion (formed from an aldehyde or ketone) with another carbonyl compound, followed by dehydration to form an α,β-unsaturated carbonyl compound. The reaction requires the presence of α-hydrogens in the starting material.

Step 2: Analyze compound A. Compound A is an α,β-unsaturated aldehyde, which can be successfully synthesized via aldol condensation. The starting materials could be acetaldehyde reacting with itself under basic conditions.

Step 3: Analyze compound B. Compound B is an α,β-unsaturated ketone. This compound can also be synthesized via aldol condensation. The starting materials could be acetone reacting with itself under basic conditions.

Step 4: Analyze compound C. Compound C is an α,β-unsaturated aldehyde with a cyclohexyl group. This compound can be synthesized via aldol condensation using cyclohexanone and acetaldehyde as starting materials. The reaction proceeds successfully because both starting materials have α-hydrogens.

Step 5: Analyze compound D and E. Compound D is an α,β-unsaturated aldehyde with a cyclohexyl group, but it has steric hindrance due to the bulky substituents, making the reaction less favorable. Compound E is an α,β-unsaturated ketone with a branched structure, which may also face steric hindrance or difficulty in enolate formation. These factors could prevent successful synthesis via aldol condensation.

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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 form an α,β-unsaturated carbonyl compound. Understanding this mechanism is crucial for predicting which compounds can be synthesized through this method.

Enolate Ion Formation

Enolate ions are formed when a base abstracts an alpha-hydrogen from a carbonyl compound, resulting in a resonance-stabilized anion. The stability of the enolate ion is influenced by the structure of the carbonyl compound and the presence of substituents. The ability to form a stable enolate is essential for successful aldol condensation, as it determines the reactivity of the starting materials.

Steric Hindrance

Steric hindrance refers to the repulsion between bulky groups in a molecule that can impede reactions. In the context of aldol condensation, steric hindrance can affect the accessibility of the carbonyl carbon to nucleophiles, thus influencing the reaction's feasibility. Compounds with significant steric hindrance may not undergo aldol condensation effectively, leading to unsuccessful syntheses.

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