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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2:32 minutes

Problem 20a

Textbook Question

What aldol addition product is formed from each of the following compounds?
a.

Verified step by step guidance

Step 1: Identify the compound provided in the image. The structure is a ketone with an aldehyde functional group, specifically 4-methylpentanal.

Step 2: Recognize the reaction conditions. The presence of NaOH and H2O indicates that this is an aldol addition reaction, which involves the formation of a β-hydroxy carbonyl compound.

Step 3: Determine the enolate formation. Under basic conditions (NaOH), the α-hydrogen adjacent to the carbonyl group is abstracted, forming an enolate ion. The enolate is stabilized by resonance between the α-carbon and the carbonyl oxygen.

Step 4: Analyze the nucleophilic attack. The enolate ion acts as a nucleophile and attacks the carbonyl carbon of another molecule of 4-methylpentanal, forming a new C-C bond. This results in the formation of a β-hydroxy aldehyde.

Step 5: Write the structure of the aldol addition product. The product will have a hydroxyl group (-OH) on the β-carbon relative to the aldehyde group, and the new C-C bond will connect the α-carbon of one molecule to the carbonyl carbon of the other.

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Key Concepts

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

Aldol Addition

Aldol addition is a reaction between two carbonyl compounds, typically aldehydes or ketones, in the presence of a base, leading to the formation of a β-hydroxy aldehyde or ketone. This reaction involves the nucleophilic attack of an enolate ion on the carbonyl carbon of another molecule, resulting in a new carbon-carbon bond. The product can further undergo dehydration to form an α,β-unsaturated carbonyl compound.

Enolate Ion Formation

Enolate ions are formed when a carbonyl compound is deprotonated at the alpha carbon by a strong base, such as NaOH. This ion is resonance-stabilized and acts as a nucleophile in aldol reactions. The ability to form enolate ions is crucial for the aldol addition process, as it allows for the nucleophilic attack on another carbonyl compound, facilitating the formation of the aldol product.

Dehydration of Aldol Products

After the aldol addition, the β-hydroxy aldehyde or ketone can undergo dehydration, where a molecule of water is eliminated, resulting in the formation of an α,β-unsaturated carbonyl compound. This step is often favored under conditions of heat or in the presence of acid or base, and it enhances the stability of the product by forming a conjugated system. Understanding this dehydration step is essential for predicting the final products of aldol reactions.

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Related Practice

Textbook Question

Describe how the following compounds can be prepared using an aldol addition in the first step of the synthesis:

Textbook Question

Describe how the following compounds can be prepared using an aldol addition in the first step of the synthesis:

Textbook Question

Identify A–C. (Hint: A shows three singlets in its 1H NMR spectrum with integral ratios 3 : 2 : 3 and gives a positive iodoform test; see Problem 58.)

Textbook Question

What aldol addition product is formed from each of the following compounds?

Textbook Question

An aldol addition can be catalyzed by acids as well as by bases. Propose a mechanism for the acid-catalyzed aldol addition of propanal.

Textbook Question

Draw the products of the following reactions:

Textbook Question

The following compounds can be synthesized by aldol condensations, followed by further reactions. (In each case, work backward from the target molecule to an aldol product, and show what compounds are needed for the condensation.)

(c)

Textbook Question

(b)

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