Textbook Question
Show how the following compounds can be made using the malonic ester synthesis.
(c) 4-phenylbutanoic acid
(d) cyclopentanecarboxylic acid
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Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
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Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 47a,b
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 47a,bChapter 22, Problem 47a,b
Show how the following compounds can be made using the malonic ester synthesis.
(a) 3-phenylpropanoic acid
(b) 2-methylpropanoic acid
Verified step by step guidance1
Step 1: Understand the malonic ester synthesis. This method involves the alkylation of diethyl malonate (a malonic ester) followed by hydrolysis and decarboxylation to produce carboxylic acids. The key steps include: (a) deprotonation of the malonic ester to form an enolate, (b) alkylation with an alkyl halide, (c) hydrolysis of the ester groups to carboxylic acids, and (d) decarboxylation to remove one carboxyl group.
Step 2: For compound (a) 3-phenylpropanoic acid, identify the alkyl halide needed for alkylation. The target structure has a phenyl group attached to a propanoic acid backbone. The alkyl halide required would be benzyl bromide (C6H5CH2Br). This will introduce the phenyl group during alkylation.
Step 3: Perform the malonic ester synthesis for (a). (a) Deprotonate diethyl malonate using a base like sodium ethoxide to form the enolate. (b) React the enolate with benzyl bromide to attach the phenyl group. (c) Hydrolyze the ester groups using aqueous acid to form the dicarboxylic acid. (d) Heat the dicarboxylic acid to decarboxylate one carboxyl group, yielding 3-phenylpropanoic acid.
Step 4: For compound (b) 2-methylpropanoic acid, identify the alkyl halide needed for alkylation. The target structure has a methyl group attached to the second carbon of a propanoic acid backbone. The alkyl halide required would be methyl iodide (CH3I). This will introduce the methyl group during alkylation.
Step 5: Perform the malonic ester synthesis for (b). (a) Deprotonate diethyl malonate using a base like sodium ethoxide to form the enolate. (b) React the enolate with methyl iodide to attach the methyl group. (c) Hydrolyze the ester groups using aqueous acid to form the dicarboxylic acid. (d) Heat the dicarboxylic acid to decarboxylate one carboxyl group, yielding 2-methylpropanoic acid.
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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 by using malonic ester as a key starting material. This reaction involves the alkylation of malonic ester followed by hydrolysis and decarboxylation, allowing for the introduction of alkyl groups and the formation of a carboxylic acid. It is particularly useful for creating compounds with a specific carbon chain length and functional groups.
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Alkylation
Alkylation is a chemical reaction that involves the transfer of an alkyl group from one molecule to another. In the context of malonic ester synthesis, the alkylation step is crucial as it introduces the desired carbon chain into the malonic ester. This process typically uses a strong base to deprotonate the ester, making it a nucleophile that can react with an alkyl halide.
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Decarboxylation
Decarboxylation is the process of removing a carboxyl group from a molecule, resulting in the release of carbon dioxide. In malonic ester synthesis, after hydrolysis of the alkylated product, decarboxylation occurs to yield the final carboxylic acid. This step is essential for obtaining the target compound with the correct structure and functional groups.
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Related Practice
Textbook Question
Show the ketones that would result from hydrolysis and decarboxylation of the following β-keto esters.
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Textbook Question
Show the resonance forms for the enolate ions that result when the following compounds are treated with a strong base.
(a) ethyl acetoacetate
(b) pentane-2,4-dione
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Textbook Question
Show how the following ketones might be synthesized by using the acetoacetic ester synthesis.
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Textbook Question
Show the resonance forms for the enolate ions that result when the following compounds are treated with a strong base.
(d) nitroacetone
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Textbook Question
Show the resonance forms for the enolate ions that result when the following compounds are treated with a strong base.
(c) ethyl α-cyanoacetate
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