Textbook Question
Identify A–C. (Hint: A shows three singlets in its 1H NMR spectrum with integral ratios 3 : 2 : 3 and gives a positive iodoform test; see Problem 58.)
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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 55b
Draw the products of the following reactions:
b. 
Verified step by step guidance1
Step 1: Identify the starting material, which is a ketone with a cyclopentane ring and a methyl group attached to the alpha-carbon.
Step 2: Recognize the reagents used in the reaction. LDA (Lithium Diisopropylamide) is a strong, non-nucleophilic base that will deprotonate the most acidic hydrogen, typically the alpha-hydrogen of the ketone. THF is the solvent, and D2O is heavy water used for deuterium exchange.
Step 3: Determine the site of deprotonation. The alpha-hydrogen adjacent to the carbonyl group is acidic due to resonance stabilization of the resulting enolate ion. LDA will remove this hydrogen, forming an enolate intermediate.
Step 4: Analyze the enolate intermediate. The enolate ion has a resonance structure where the negative charge is delocalized between the alpha-carbon and the oxygen atom of the carbonyl group.
Step 5: Predict the final product. The enolate reacts with D2O, leading to the replacement of the alpha-hydrogen with a deuterium atom (D). The final product is the deuterium-labeled ketone.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enolate Formation
Enolate formation is a key step in organic reactions involving carbonyl compounds. It occurs when a base, such as LDA (Lithium diisopropylamide), abstracts an alpha hydrogen from a carbonyl compound, resulting in the formation of an enolate ion. This ion is resonance-stabilized and can act as a nucleophile in subsequent reactions, allowing for the formation of new carbon-carbon bonds.
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Formation of Enolates
Deuteration
Deuteration is the process of replacing hydrogen atoms in a molecule with deuterium, a heavier isotope of hydrogen. In the context of the reaction shown, the use of D2O (deuterated water) allows for the incorporation of deuterium into the enolate product. This is significant in mechanistic studies and can help trace reaction pathways or confirm the formation of specific intermediates.
Reaction Conditions
The reaction conditions, including the solvent (THF) and temperature (0°C), play a crucial role in the outcome of organic reactions. THF is a polar aprotic solvent that stabilizes the enolate ion, while the low temperature helps control the reaction rate and minimize side reactions. Understanding these conditions is essential for predicting the products and optimizing yields in synthetic organic chemistry.
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Related Practice
Textbook Question
Draw the products of the following reactions:
a.
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Textbook Question
Draw the products of the following reactions:
d. diethyl 1,2-benzenedicarboxylate + sodium ethoxide: (1) slow addition of ethyl acetate; (2) HCl
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Textbook Question
An aldol addition can be catalyzed by acids as well as by bases. Propose a mechanism for the acid-catalyzed aldol addition of propanal.
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Textbook Question
Which of the following compounds decarboxylates when heated?
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Textbook Question
In the presence of excess base and excess halogen, a methyl ketone is converted to a carboxylate ion. The reaction is known as the haloform reaction because one of the products is haloform (chloroform, bromoform, or iodoform). Before spectroscopy became a routine analytical tool, the haloform reaction served as a test for methyl ketones: the formation of iodoform, a bright yellow compound, signaled that a methyl ketone was present. Why do only methyl ketones form a haloform?
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