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

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Malonic Ester Synthesis

Organic Chemistry

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Malonic Ester Synthesis

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6:56 minutes

Problem 49e

Textbook Question

Draw the products of the following reactions: e. diethyl malonate: (1) sodium ethoxide; (2) isobutyl bromide; (3) HCl, H₂O + heat

Verified step by step guidance

Step 1: Analyze the starting material, diethyl malonate. It contains two ester groups and a methylene group (-CH2-) between them, which is acidic due to the electron-withdrawing effects of the ester groups. This makes the methylene hydrogens susceptible to deprotonation by a base.

Step 2: In the first step, sodium ethoxide (CH3CH2ONa) acts as a strong base to deprotonate the methylene group of diethyl malonate, forming a carbanion. This carbanion is stabilized by resonance with the two ester groups.

Step 3: In the second step, the carbanion undergoes nucleophilic substitution with isobutyl bromide. The carbanion attacks the electrophilic carbon in the isobutyl bromide, displacing the bromide ion and forming a new C-C bond. This results in an alkylated diethyl malonate derivative.

Step 4: In the third step, the reaction mixture is treated with HCl, H2O, and heat. Under these conditions, the ester groups undergo hydrolysis to form carboxylic acids. The intermediate then undergoes decarboxylation (loss of CO2) due to heating, leaving behind a single carboxylic acid product.

Step 5: The final product is a substituted carboxylic acid where the original methylene group has been alkylated with the isobutyl group. The decarboxylation step ensures that only one carboxylic acid group remains in the product.

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Key Concepts

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

Malonic Ester Synthesis

Malonic ester synthesis is a method for synthesizing carboxylic acids through the alkylation of diethyl malonate. In this reaction, diethyl malonate is first deprotonated by a strong base, such as sodium ethoxide, to form a nucleophilic enolate. This enolate can then react with an alkyl halide, such as isobutyl bromide, to form a substituted malonic ester, which can be hydrolyzed and decarboxylated to yield the desired carboxylic acid.

Enolate Formation

Enolate formation is a crucial step in many organic reactions, particularly in malonic ester synthesis. When a compound with an acidic hydrogen, like diethyl malonate, is treated with a strong base, it loses a proton to form an enolate ion. This enolate is a resonance-stabilized species that can act as a nucleophile, allowing it to attack electrophiles such as alkyl halides, facilitating the formation of new carbon-carbon bonds.

Hydrolysis and Decarboxylation

Hydrolysis and decarboxylation are key processes that follow the alkylation step in malonic ester synthesis. After the alkylation, the product is treated with acid and water, leading to hydrolysis, which converts the ester into a carboxylic acid. Subsequently, heating the carboxylic acid can induce decarboxylation, where carbon dioxide is released, resulting in the formation of a more stable product, typically a ketone or a simple carboxylic acid.

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Related Practice

Textbook Question

What amino acid is formed using the N-phthalimidomalonic ester synthesis when the following alkyl halides are used in the third step?

Textbook Question

What amino acid is formed using the N-phthalimidomalonic ester synthesis when the following alkyl halides are used in the third step?

b. CH₃SCH₂CH₂Br

Multiple Choice

Provide the major product for the following reaction

Multiple Choice

Provide the major product for the following reaction

Textbook Question

Explain why the following carboxylic acids cannot be prepared by a malonic ester synthesis:

Textbook Question

b. What carboxylic acid is formed when the malonic ester synthesis is carried out with two equivalents of malonic ester, one equivalent of 1,5-dibromopentane, and two equivalents of base?

Textbook Question

Amobarbital is a sedative marketed under the trade name Amytal. Propose a synthesis of amobarbital, using diethyl malonate and urea as two of the starting materials.

Textbook Question

Show how the following compounds can be made using the malonic ester synthesis.

(a) 3-phenylpropanoic acid

(b) 2-methylpropanoic acid

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