Textbook Question
Esters with only one α hydrogen generally give poor yields in the Claisen condensation. Propose a mechanism for the Claisen condensation of ethyl isobutyrate, and explain why a poor yield is obtained.
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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 33a
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 33aChapter 22, Problem 33a
The following compound results from base-catalyzed aldol cyclization of a 2-substituted cyclohexanone.
(a) Show the diketone that would cyclize to give this product.
Verified step by step guidance1
Step 1: Analyze the given product structure. The compound is a bicyclic ketone with a cyclohexane ring fused to a cyclopentane ring. The ketone group is located on the cyclopentane ring.
Step 2: Recall the mechanism of base-catalyzed aldol cyclization. This reaction involves the formation of a new carbon-carbon bond between two carbonyl groups, typically resulting in a cyclic structure.
Step 3: Identify the diketone precursor. To form the bicyclic structure, the diketone must have two carbonyl groups positioned such that they can undergo intramolecular aldol condensation. In this case, the precursor would be a 2-substituted cyclohexanone with a second ketone group at the appropriate position.
Step 4: Draw the diketone structure. The diketone should have one ketone group on the cyclohexane ring and another ketone group on the side chain at the position that allows cyclization to form the five-membered ring.
Step 5: Verify the connectivity. Ensure that the diketone structure aligns with the product after cyclization, considering the formation of the new bond and the elimination of water during the aldol condensation.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Aldol Condensation
Aldol condensation is a fundamental reaction in organic chemistry where an enolate ion reacts with a carbonyl compound to form a β-hydroxy aldehyde or ketone. This reaction can occur intramolecularly, leading to the formation of cyclic compounds. The process typically involves a base that deprotonates the carbon adjacent to the carbonyl, generating the enolate, which then attacks the carbonyl carbon of another molecule.
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Cyclization
Cyclization refers to the process of forming a cyclic compound from a linear precursor. In the context of aldol reactions, intramolecular cyclization occurs when a diketone or a similar compound undergoes a reaction where the nucleophile and electrophile are part of the same molecule, leading to the formation of a ring structure. This is significant in synthesizing complex cyclic molecules, often seen in natural products and pharmaceuticals.
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Diketones
Diketones are organic compounds containing two carbonyl groups (C=O) within the same molecule. They can serve as precursors in aldol reactions, where one carbonyl group can form an enolate and react with the other carbonyl group to create a cyclic structure. Understanding the structure and reactivity of diketones is crucial for predicting the products of aldol cyclization and for designing synthetic pathways in organic chemistry.
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Related Practice
Textbook Question
The following compound results from base-catalyzed aldol cyclization of a 2-substituted cyclohexanone.
(b) Propose a mechanism for the cyclization.
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Textbook Question
Ethoxide is used as the base in the condensation of ethyl acetate to avoid some unwanted side reactions. Show what side reactions would occur if the following bases were used.
(a) sodium methoxide
(b) sodium hydroxide
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Textbook Question
Show how each compound can be dissected into reagents joined by an aldol condensation, then decide whether the necessary aldol condensation is feasible.
(e)
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Textbook Question
Show how each compound can be dissected into reagents joined by an aldol condensation, then decide whether the necessary aldol condensation is feasible.
(b)
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Textbook Question
Show how each compound can be dissected into reagents joined by an aldol condensation, then decide whether the necessary aldol condensation is feasible.
(c)
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