Textbook Question
Propose mechanisms for the two Dieckmann condensations just shown.
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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 39b
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 39bChapter 22, Problem 39b
Propose mechanisms for the two Dieckmann condensations just shown.
Verified step by step guidance1
Step 1: Identify the starting materials for the Dieckmann condensation. In the first reaction, the starting material is diethyl adipate (a 1,6-diesters), and in the second reaction, the starting material is dimethyl pimelate (a 1,7-diesters). Both are diesters capable of undergoing intramolecular condensation.
Step 2: Recognize the role of the base. The base used in the reaction is ethoxide ion (\( \text{CH}_3\text{CH}_2\text{O}^- \)). This base abstracts a proton from the alpha-carbon (\( \alpha \)) of one ester group, generating an enolate ion.
Step 3: Understand the nucleophilic attack. The enolate ion formed in Step 2 acts as a nucleophile and attacks the carbonyl carbon of the second ester group within the same molecule. This intramolecular reaction forms a cyclic intermediate.
Step 4: Analyze the intermediate. The cyclic intermediate undergoes elimination of the ethoxide group (\( \text{CH}_3\text{CH}_2\text{O}^- \)), resulting in the formation of a cyclic \( \beta \)-keto ester. For diethyl adipate, a five-membered ring is formed, while for dimethyl pimelate, a six-membered ring is formed.
Step 5: Confirm the product. The final products are cyclic \( \beta \)-keto esters. For diethyl adipate, the product is a five-membered cyclic \( \beta \)-keto ester, and for dimethyl pimelate, the product is a six-membered cyclic \( \beta \)-keto ester. These products are stabilized by resonance between the keto and ester groups.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Dieckmann Condensation
The Dieckmann condensation is a reaction involving the intramolecular condensation of diesters to form cyclic β-keto esters. This reaction typically occurs under basic conditions, where a base deprotonates an α-hydrogen, allowing the resulting enolate to attack the carbonyl carbon of another ester group. The process results in the formation of a five- or six-membered ring, depending on the distance between the ester groups.
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Diesters (Dieckmann Condensation)
Enolate Formation
Enolate formation is a crucial step in many carbonyl chemistry reactions, including the Dieckmann condensation. In this process, a base abstracts an α-hydrogen from a carbonyl compound, generating a resonance-stabilized enolate ion. This enolate can then act as a nucleophile, attacking electrophilic centers, such as carbonyl carbons, facilitating the formation of new carbon-carbon bonds.
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Cyclic β-Keto Esters
Cyclic β-keto esters are compounds formed from the Dieckmann condensation, characterized by a cyclic structure containing both a ketone and an ester functional group. These compounds are significant in organic synthesis due to their reactivity and ability to undergo further transformations. The presence of both functional groups allows for diverse chemical reactivity, making them valuable intermediates in the synthesis of various organic molecules.
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Related Practice
Textbook Question
Some (but not all) of the following keto esters can be formed by Dieckmann condensations. Determine which ones are possible, and draw the starting diesters.
(c)
(d)
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Textbook Question
Some (but not all) of the following keto esters can be formed by Dieckmann condensations. Determine which ones are possible, and draw the starting diesters.
(a)
(b)
1
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Textbook Question
Show what esters would undergo Claisen condensation to give the following β-keto esters.
(b)
1
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Textbook Question
Some (but not all) of the following keto esters can be formed by Dieckmann condensations. Determine which ones are possible, and draw the starting diesters.
Textbook Question
Show what esters would undergo Claisen condensation to give the following β-keto esters.
(c)
2
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