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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Problem 44a

Textbook Question

Predict the major products of the following crossed Claisen condensations.
(a)

Verified step by step guidance

Step 1: Understand the Claisen condensation reaction. A Claisen condensation involves the reaction between two esters or one ester and a ketone in the presence of a strong base, typically an alkoxide, to form a β-keto ester or β-diketone. Crossed Claisen condensations occur between two different esters or an ester and a ketone.

Step 2: Identify the reactants in the crossed Claisen condensation. Determine which compounds are involved in the reaction and note their functional groups (e.g., ester or ketone). This will help predict the nucleophile and electrophile in the reaction.

Step 3: Determine the nucleophile. The nucleophile is typically the enolate ion formed from the compound with the most acidic α-hydrogen. Use the base to deprotonate the α-hydrogen adjacent to the carbonyl group, forming the enolate ion. Represent this step using MathML:

{CH}_{2} (COOR) - \to {CH}_{2} (COOR) -

Step 4: Identify the electrophile. The electrophile is the carbonyl carbon of the other ester or ketone. The enolate ion attacks the electrophilic carbonyl carbon, leading to the formation of a new C-C bond. Represent this step using MathML:

R - COOR \to R - CO (CH - COOR)

Step 5: Predict the major product. After the nucleophilic attack, the intermediate undergoes protonation and elimination of the alkoxide group to form the final β-keto ester or β-diketone product. Consider steric and electronic factors to predict the major product of the reaction.

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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, typically sodium ethoxide. This reaction results in the formation of a β-keto ester or a β-diketone. Understanding this mechanism is crucial for predicting the products, as it involves nucleophilic attack and subsequent elimination of an alcohol.

Crossed Claisen Condensation

Crossed Claisen condensation refers to a variation of the Claisen reaction where two different carbonyl compounds are used. This can lead to a mixture of products, making it essential to consider the reactivity and sterics of the reactants. The major product is typically the one formed from the more reactive ester or carbonyl compound, which can help in predicting the outcome of the reaction.

Regioselectivity

Regioselectivity in organic reactions refers to the preference of a chemical reaction to occur at one location over another in a molecule. In the context of crossed Claisen condensations, understanding which carbonyl compound is more likely to react and where the nucleophilic attack will occur is vital for predicting the major product. Factors such as steric hindrance and electronic effects play significant roles in determining regioselectivity.

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Predict the major products of the following crossed Claisen condensations. (a)

Key Concepts

Claisen Condensation

Crossed Claisen Condensation

Regioselectivity

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Predict the major products of the following crossed Claisen condensations.
(a)