Textbook Question
Predict the products of aldol condensation, followed by dehydration, of the following ketones and aldehydes.
(a) butyraldehyde
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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 24c
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 24cChapter 22, Problem 24c
Predict the products of aldol condensation, followed by dehydration, of the following ketones and aldehydes.
(c) cyclohexanone
Verified step by step guidance1
Identify the reactants: Cyclohexanone is a ketone with a six-membered ring. In an aldol condensation, it will act as both the nucleophile and electrophile due to the presence of alpha-hydrogens.
Determine the enolate formation: Deprotonate one of the alpha-hydrogens of cyclohexanone using a base (e.g., hydroxide ion) to form the enolate ion. The enolate ion is stabilized by resonance between the alpha-carbon and the carbonyl oxygen.
Perform the nucleophilic attack: The enolate ion acts as a nucleophile and attacks the carbonyl carbon of another cyclohexanone molecule, forming a beta-hydroxyketone intermediate. This step is the aldol addition.
Facilitate dehydration: Under heating or with a strong base, the beta-hydroxyketone undergoes elimination of water (dehydration) to form an α,β-unsaturated ketone. This involves the removal of a hydroxyl group and an alpha-hydrogen, resulting in the formation of a double bond between the alpha and beta carbons.
Predict the final product: The final product of the reaction is an α,β-unsaturated ketone derived from cyclohexanone. Specifically, it will be 2-cyclohexenone, which contains a conjugated double bond in the six-membered ring.
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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 reaction between aldehydes or ketones that contain at least one alpha-hydrogen. In this process, one molecule acts as a nucleophile and attacks the carbonyl carbon of another molecule, forming a beta-hydroxy carbonyl compound (aldol). This intermediate can then undergo dehydration to yield an alpha, beta-unsaturated carbonyl compound, which is often more stable and reactive.
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Dehydration Reaction
Dehydration is the elimination of water from a compound, often occurring in organic reactions to form double bonds. In the context of aldol condensation, after the formation of the aldol product, dehydration involves the removal of a water molecule, resulting in the formation of a conjugated enone or enal. This step is crucial as it enhances the stability and reactivity of the final product.
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Cyclohexanone Reactivity
Cyclohexanone is a cyclic ketone that can participate in aldol condensation due to the presence of alpha-hydrogens. Its reactivity is influenced by the ring structure, which can affect steric hindrance and the stability of intermediates. Understanding how cyclohexanone reacts in aldol condensation helps predict the products formed, including the potential for intramolecular reactions if conditions allow.
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Related Practice
Textbook Question
Propose mechanisms for the following base-catalyzed condensations, with dehydration.
(a) 2,2-dimethylpropanal with acetaldehyde
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Textbook Question
Predict the products of aldol condensation, followed by dehydration, of the following ketones and aldehydes.
(b) acetophenone
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Textbook Question
Propose a mechanism for the dehydration of diacetone alcohol to mesityl oxide
(a) in acid.
(b) in base.
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Textbook Question
Predict the major products of the following base-catalyzed aldol condensations with dehydration.
(a) benzophenone (PhCOPh) + propionaldehyde
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Textbook Question
Propose mechanisms for the following base-catalyzed condensations, with dehydration.
(b) benzaldehyde with propionaldehyde
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