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

Previous problemNext problem

3:11 minutes

Problem 64c

Textbook Question

Propose mechanisms for the reactions shown in Problems 22-63 part (a).

Verified step by step guidance

Step 1: Analyze the reactants and reagents. The starting material is an ester (methyl ester) with a ketone group adjacent to it. The reagent is methoxide ion (CH3O⁻) in methanol (CH3OH), which acts as a nucleophile and base.

Step 2: Identify the reaction type. This reaction involves nucleophilic attack and likely enolate formation due to the presence of the ketone group. Methoxide ion can deprotonate the alpha-hydrogen of the ketone, forming an enolate intermediate.

Step 3: Mechanism initiation. Methoxide ion deprotonates the alpha-hydrogen of the ketone, forming a resonance-stabilized enolate ion. The enolate ion is nucleophilic and can attack the ester carbonyl carbon.

Step 4: Nucleophilic attack. The enolate ion attacks the carbonyl carbon of the ester group, leading to the formation of a tetrahedral intermediate. This intermediate collapses, expelling the methoxide group (CH3O⁻) and forming a new carbon-carbon bond.

Step 5: Final product formation. The reaction results in a β-keto ester, where the ketone and ester groups are separated by one carbon atom. This product is stabilized by resonance between the ketone and ester functionalities.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. In this context, the methoxide ion (−OCH3) acts as a nucleophile, attacking the electrophilic carbon atom of the carbonyl group. Understanding the mechanism of nucleophilic substitution is crucial for predicting the products of the reaction shown.

Mechanism of Aldol Reactions

Aldol reactions involve the formation of β-hydroxy aldehydes or ketones through the reaction of enolates with carbonyl compounds. The reaction depicted may involve an aldol condensation, where the initial product can further dehydrate to form an α,β-unsaturated carbonyl compound. Recognizing the steps of aldol reactions is essential for proposing accurate mechanisms.

Electrophilicity and Reactivity of Carbonyl Compounds

Carbonyl compounds, such as aldehydes and ketones, exhibit electrophilic character due to the partial positive charge on the carbon atom adjacent to the oxygen. This electrophilicity makes them susceptible to nucleophilic attack, which is a key aspect of the reaction mechanism. Understanding the reactivity of carbonyls is vital for predicting how they will interact with nucleophiles.

Watch next

Master General Features with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

Textbook Question

Show how each compound can be dissected into reagents joined by an aldol condensation, then decide whether the necessary aldol condensation is feasible.

(c)

Textbook Question

The Knoevenagel condensation is a special case of the aldol condensation in which an active methylene compound reacts with an aldehyde or ketone, in the presence of a secondary amine as a basic catalyst, to produce a new C=C. Show the starting materials that made each of these by a Knoevenagel condensation.

(d)

Textbook Question

(e)

Textbook Question

(f)

Textbook Question

Predict the products of these reaction sequences.

Textbook Question

Show how you would use an aldol, Claisen, or another type of condensation to make each compound.

(c)

Textbook Question

Propose mechanisms for the reactions shown in Problems 22-62 part (a).

Textbook Question

Many of the condensations we have studied are reversible. The reverse reactions are often given the prefix retro-, the Latin word meaning “backward.” Propose mechanisms to account for the following reactions.

(a)

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap