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

Claisen Condensation

Organic Chemistry

25. Condensation Chemistry

Claisen Condensation

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6:45 minutes

Problem 29a

Textbook Question

Which of the following esters cannot undergo a Claisen condensation?

Verified step by step guidance

Step 1: Recall the requirements for a Claisen condensation. Claisen condensation involves the reaction of two ester molecules or one ester and one ketone molecule in the presence of a strong base, typically an alkoxide. The reaction requires the ester to have at least one alpha-hydrogen (a hydrogen atom attached to the carbon adjacent to the carbonyl group). This alpha-hydrogen is necessary for enolate formation, which is a key intermediate in the reaction.

Step 2: Analyze the structure of ester A. Ester A has an alpha-carbon with hydrogens attached, making it capable of forming an enolate. Therefore, ester A can undergo Claisen condensation.

Step 3: Analyze the structure of ester B. Ester B also has an alpha-carbon with hydrogens attached, allowing enolate formation. Thus, ester B can undergo Claisen condensation.

Step 4: Analyze the structure of ester C. Ester C has an alpha-carbon with hydrogens attached, which means it can form an enolate and participate in Claisen condensation.

Step 5: Analyze the structure of ester D. Ester D has a nitro group (-NO2) attached to the aromatic ring. This electron-withdrawing group significantly reduces the acidity of the alpha-hydrogens, making enolate formation difficult or impossible. Therefore, ester D cannot undergo Claisen condensation.

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Key Concepts

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

Claisen Condensation

Claisen condensation is a reaction between two esters or an ester and a carbonyl compound in the presence of a strong base, leading to the formation of a β-keto ester or a β-diketone. This reaction requires at least one of the reactants to have an alpha hydrogen, which is essential for the formation of the enolate ion that initiates the reaction.

Alpha Hydrogen

Alpha hydrogens are the hydrogen atoms attached to the carbon atom adjacent to a carbonyl group. Their presence is crucial for reactions like Claisen condensation, as they can be deprotonated by a strong base to form an enolate ion, which is a reactive intermediate that facilitates the condensation process.

Steric Hindrance

Steric hindrance refers to the repulsion between bulky groups in a molecule that can impede chemical reactions. In the context of Claisen condensation, steric hindrance can prevent the formation of the enolate ion or hinder the approach of reactants, making certain esters less reactive or unable to participate in the reaction.

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