Textbook Question
How could each of the following compounds be prepared from a ketone and an alkyl halide?
a.
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Ch. 17 - Reactions at the Alpha-Carbon
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 18, Problem 7f
Draw the enol tautomers for each of the following compounds. For compounds that have more than one enol tautomer, indicate the one that is more stable.
f. 
Verified step by step guidance1
Step 1: Identify the keto group in the compound. The keto group is the carbonyl group (C=O) attached to the ring structure.
Step 2: Recall the concept of keto-enol tautomerism. This is an equilibrium process where a hydrogen atom shifts from an alpha-carbon (adjacent to the carbonyl group) to the oxygen atom of the carbonyl group, forming an enol (a compound with a hydroxyl group attached to a double-bonded carbon).
Step 3: Locate the alpha-hydrogens in the compound. These are hydrogens attached to the carbons adjacent to the carbonyl group. In this case, there are alpha-hydrogens on both sides of the carbonyl group.
Step 4: Draw the possible enol tautomers. For each alpha-hydrogen, move the hydrogen to the oxygen atom of the carbonyl group and form a double bond between the alpha-carbon and the carbonyl carbon. This will result in two possible enol tautomers.
Step 5: Determine the more stable enol tautomer. Stability is influenced by factors such as conjugation and hydrogen bonding. In this case, the enol tautomer that forms a conjugated system with the aromatic ring is more stable due to resonance stabilization.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Tautomerization
Tautomerization is a chemical reaction that involves the transfer of a proton and a shift of a double bond, resulting in the interconversion between two isomers known as tautomers. In organic chemistry, this often occurs between keto and enol forms, where the keto form contains a carbonyl group (C=O) and the enol form has a hydroxyl group (–OH) adjacent to a double bond. Understanding this process is crucial for predicting the stability and reactivity of compounds.
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Tautomerization Mechanisms
Enol Stability
The stability of enol tautomers can vary significantly based on factors such as intramolecular hydrogen bonding, steric hindrance, and resonance stabilization. Enols that can form strong hydrogen bonds or have resonance structures that delocalize charge are generally more stable. Recognizing these factors helps in determining which enol tautomer is favored in a given reaction or compound.
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Keto-Enol Equilibrium
Keto-enol equilibrium refers to the dynamic balance between the keto and enol forms of a compound. The position of this equilibrium is influenced by temperature, solvent, and the presence of catalysts. In many cases, the keto form is more thermodynamically stable, but under certain conditions, the enol form may be favored, especially in reactions involving electrophiles or nucleophiles. Understanding this equilibrium is essential for predicting the behavior of organic compounds in various chemical contexts.
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Related Practice
Textbook Question
Show how the following compounds can be prepared from the given starting material:
a.
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Textbook Question
Draw the enol tautomers for each of the following compounds. For compounds that have more than one enol tautomer, indicate the one that is more stable.
d.
e.
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Textbook Question
A ketone undergoes acid-catalyzed bromination, acid-catalyzed chlorination, racemization, and acid-catalyzed deuterium exchange at the ⍺-carbon. All of these reactions have similar rate constants.What does this tell you about the mechanisms of these reactions?
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Textbook Question
Rank the compounds in each of the following groups from strongest acid to weakest acid:
c.
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Textbook Question
Explain why 92% of 2,4-pentanedione exists as the enol tautomer in hexane but only 15% of this compound exists as the enol tautomer in water.
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