Textbook Question
Using cyclopentanone as the reactant, show the product of
b. an aldol addition.
c. an aldol condensation.
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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 59a,b,c
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.)
Verified step by step guidance1
Step 1: Analyze the given hint and the reaction sequence. The hint mentions that compound A shows three singlets in its 1H NMR spectrum with integral ratios 3:2:3 and gives a positive iodoform test. A positive iodoform test indicates the presence of a methyl ketone group (CH3-C=O). The NMR data suggests three distinct environments for protons, likely corresponding to methyl groups, a CH2 group, and another methyl group.
Step 2: Examine the reaction sequence. Compound I (C11H20O3) undergoes hydrolysis in acidic conditions (HCl, H2O, Δ) to form compound II. Acidic hydrolysis typically breaks ester bonds, forming carboxylic acids or alcohols. Compound II then undergoes hydrolysis in basic conditions (HO-, H2O), which could further cleave ester or amide bonds.
Step 3: Compound III is formed after the basic hydrolysis of II. Compound III is then subjected to acidic conditions (HCl, Δ), which may lead to decarboxylation or further hydrolysis. This sequence suggests that the reactions are progressively simplifying the structure, possibly leading to smaller molecules.
Step 4: Based on the hint and the reaction sequence, compound A (likely derived from III or IV) must contain a methyl ketone group to give a positive iodoform test. The NMR data (3:2:3 singlets) suggests a symmetrical structure with distinct proton environments. Consider the possibility of acetone or a similar compound as A.
Step 5: To identify compounds B and C, trace the intermediates formed during the reaction sequence. Compound B is likely the product of the first hydrolysis step, and compound C is the product of the second hydrolysis step. Use the molecular formula and reaction conditions to deduce their structures, keeping in mind the functional groups involved (esters, carboxylic acids, alcohols, etc.).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
NMR Spectroscopy
Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It provides information about the number of hydrogen atoms in different environments, represented by peaks in the spectrum. The integral ratios of these peaks indicate the relative number of protons contributing to each signal, which is crucial for identifying molecular structure.
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General NMR Features
Iodoform Test
The iodoform test is a qualitative reaction used to identify methyl ketones and certain alcohols. When a compound containing a methyl group adjacent to a carbonyl group is treated with iodine and a base, it produces a yellow precipitate of iodoform (CHI3). A positive result indicates the presence of a specific structural feature, aiding in the identification of the compound in question.
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Aldol Condensation
Aldol condensation is a fundamental reaction in organic chemistry where aldehydes or ketones with alpha-hydrogens react in the presence of a base to form beta-hydroxy aldehydes or ketones. This reaction can further dehydrate to yield α,β-unsaturated carbonyl compounds. Understanding this mechanism is essential for analyzing reaction pathways and predicting the products of complex organic transformations.
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Related Practice
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
Draw the products of the following reactions:
b.
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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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Textbook Question
Show how 4-methyl-3-hexanol can be synthesized from 3-pentanone.
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Textbook Question
Using cyclopentanone as the reactant, show the product of a. acid-catalyzed keto–enol interconversion.
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