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 24b
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 24bChapter 22, Problem 24b
Predict the products of aldol condensation, followed by dehydration, of the following ketones and aldehydes.
(b) acetophenone
Verified step by step guidance1
Identify the structure of acetophenone. Acetophenone is a ketone with the structure C6H5-CO-CH3, where the carbonyl group (C=O) is directly attached to a benzene ring.
Determine the enolate ion formation. Under basic conditions, the alpha-hydrogen (hydrogen attached to the carbon adjacent to the carbonyl group) of acetophenone is abstracted by a base, forming an enolate ion. The enolate ion is resonance-stabilized, with the negative charge delocalized between the alpha-carbon and the oxygen atom of the carbonyl group.
Perform the aldol addition. The enolate ion acts as a nucleophile and attacks the carbonyl carbon of another molecule of acetophenone. This forms a beta-hydroxyketone intermediate, where the hydroxyl group (-OH) is attached to the beta-carbon relative to the original carbonyl group.
Carry out the dehydration step. Under heating or acidic/basic conditions, the beta-hydroxyketone undergoes elimination of water (dehydration) to form an α,β-unsaturated ketone. This involves the removal of the hydroxyl group and a hydrogen atom from the alpha-carbon, resulting in the formation of a double bond between the alpha and beta carbons.
Predict the final product. The final product of the aldol condensation followed by dehydration of acetophenone is an α,β-unsaturated ketone with the structure C6H5-CH=CH-CO-CH3, where the double bond is conjugated with both the benzene ring and the carbonyl group, providing additional stability.
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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 the final product of the reaction.
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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, leading to the formation of a more stable alpha, beta-unsaturated carbonyl compound. This step is crucial as it enhances the reactivity and stability of the final product.
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Acetophenone Structure
Acetophenone is an aromatic ketone with the formula C8H8O, consisting of a phenyl group attached to a carbonyl group (C=O). Its structure includes an alpha-hydrogen, making it a suitable candidate for aldol condensation. Understanding its structure is essential for predicting the products of the reaction, as the position of the carbonyl and the presence of the aromatic ring influence the reactivity and the nature of the final products.
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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
Propose a complete mechanism for the acid-catalyzed aldol condensation of acetone.
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Textbook Question
Predict the products of aldol condensation, followed by dehydration, of the following ketones and aldehydes.
(c) cyclohexanone
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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
Propose mechanisms for the following base-catalyzed condensations, with dehydration.
(b) benzaldehyde with propionaldehyde
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