Textbook Question
The following compound results from base-catalyzed aldol cyclization of a 2-substituted cyclohexanone.
(b) Propose a mechanism for the cyclization.
1
views
Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds
Wade9th EditionOrganic ChemistryISBN: 9780135213728
Not the one you use?Change textbookSelect a different textbook
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
All textbooks
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 32c
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 32cChapter 22, Problem 32c
Show how each compound can be dissected into reagents joined by an aldol condensation, then decide whether the necessary aldol condensation is feasible.
(c) 
Verified step by step guidance1
Step 1: Identify the product of the aldol condensation. The given compound contains a β-hydroxy ketone structure that has undergone dehydration to form an α,β-unsaturated ketone. This indicates it is the result of an aldol condensation followed by elimination of water.
Step 2: Break the compound into two potential reagents. In an aldol condensation, one reagent acts as the enolate ion (nucleophile) and the other as the carbonyl compound (electrophile). Here, the compound can be dissected into benzaldehyde (PhCHO) and acetone (CH3COCH3).
Step 3: Analyze the feasibility of forming the enolate. Acetone can form an enolate ion under basic conditions because it has acidic α-hydrogens adjacent to the carbonyl group. This enolate can attack the electrophilic carbonyl carbon of benzaldehyde.
Step 4: Consider the aldol addition step. The enolate ion of acetone will attack the carbonyl carbon of benzaldehyde, forming a β-hydroxy ketone intermediate. This intermediate is stable under basic conditions.
Step 5: Evaluate the dehydration step. Under heating or continued basic conditions, the β-hydroxy ketone intermediate undergoes elimination of water to form the α,β-unsaturated ketone product shown in the image. This dehydration step is feasible and commonly occurs in aldol condensations.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
3mWas this helpful?
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 alpha-hydrogens, leading to the formation of β-hydroxy aldehydes or ketones. This reaction involves the nucleophilic addition of an enolate ion to a carbonyl carbon, followed by dehydration to form an α,β-unsaturated carbonyl compound. Understanding this mechanism is crucial for dissecting compounds into their respective reagents.
Recommended video:
Guided course
09:51
Crossed Aldol
Enolate Ion Formation
Enolate ions are formed when a base abstracts an alpha-hydrogen from a carbonyl compound, resulting in a resonance-stabilized anion. This ion acts as a nucleophile in aldol reactions, allowing it to attack another carbonyl compound. Recognizing how to generate enolate ions from the given compounds is essential for determining the feasibility of the aldol condensation.
Recommended video:
Guided course
02:26Formation of Enolates
Feasibility of Aldol Condensation
The feasibility of an aldol condensation depends on the stability of the resulting products and the reaction conditions. Factors such as steric hindrance, electronic effects, and the presence of suitable bases or acids influence whether the reaction will proceed. Evaluating these factors helps in deciding if the aldol condensation can occur with the given compounds.
Recommended video:
Guided course
09:51Crossed Aldol
Related Practice
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.
(a)
5
views
Textbook Question
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.
2
views
Textbook Question
When cyclodecane-1,6-dione is treated with sodium carbonate, the product gives a UV spectrum similar to that of 1-acetyl-2-methylcyclopentene. Propose a structure for the product, and give a mechanism for its formation.
1
views
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)
1
views
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)
2
views