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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1:35 minutes

Problem 43b

Textbook Question

Show how crossed Claisen condensations could be used to prepare the following esters.
(b)

Verified step by step guidance

Step 1: Identify the ester product and analyze its structure. The given ester contains two ester functional groups (-COOCH3) and a phenyl group (Ph) attached to a central carbon. This suggests that the product could be formed via a crossed Claisen condensation between two different esters.

Step 2: Determine the two esters required for the crossed Claisen condensation. One ester should provide the phenyl group (Ph) and the alpha-hydrogen for enolate formation, while the other ester should provide the second ester group. For this product, methyl benzoate (PhCOOCH3) and dimethyl malonate (CH2(CO2CH3)2) are suitable reactants.

Step 3: Describe the mechanism of the crossed Claisen condensation. In the presence of a strong base (e.g., sodium ethoxide, NaOEt), the alpha-hydrogen of dimethyl malonate is deprotonated to form an enolate ion. This enolate then attacks the carbonyl carbon of methyl benzoate, leading to the formation of a new carbon-carbon bond.

Step 4: Explain the intermediate and subsequent steps. After the nucleophilic attack, a tetrahedral intermediate is formed, which collapses to expel the methoxide ion (CH3O−). This results in the formation of a β-keto ester intermediate.

Step 5: Highlight the final product formation. The β-keto ester intermediate undergoes protonation to yield the final ester product shown in the image. Ensure that the reaction conditions (base, solvent, and temperature) are carefully controlled to favor the crossed Claisen condensation and minimize side reactions.

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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 is crucial for forming carbon-carbon bonds and is widely used in organic synthesis to create complex molecules.

Crossed Claisen Condensation

Crossed Claisen condensation involves the reaction of two different esters or an ester with a carbonyl compound, allowing for greater diversity in the products formed. This method is particularly useful when one of the reactants has no alpha-hydrogens, preventing self-condensation and enabling the formation of specific products, such as the esters shown in the question.

Reactivity of Esters

Esters are reactive compounds in organic chemistry, particularly due to the presence of the carbonyl group, which is susceptible to nucleophilic attack. Understanding the reactivity of esters, including their ability to undergo Claisen condensation, is essential for predicting the outcomes of reactions and designing synthetic pathways for desired compounds.

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Show how crossed Claisen condensations could be used to prepare the following esters.(b)

Key Concepts

Claisen Condensation

Crossed Claisen Condensation

Reactivity of Esters

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Show how crossed Claisen condensations could be used to prepare the following esters.
(b)