Textbook Question
Determine the structures of compounds A through G, including stereochemistry where appropriate.
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Ch.10 - Structure and Synthesis of Alcohols
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
Chapter 10, Problem 46c
Vinyl alcohols are generally unstable, quickly isomerizing to carbonyl compounds. Propose mechanisms for the following isomerizations.
(c) 
Verified step by step guidance1
Step 1: Recognize that the vinyl alcohol (enol) isomerizes to a ketone through a keto-enol tautomerization mechanism. This process is catalyzed by either acid or base.
Step 2: In the base-catalyzed mechanism, hydroxide (-OH) acts as a catalyst. The hydroxide ion abstracts the acidic proton from the hydroxyl group of the enol, forming a negatively charged oxygen (alkoxide ion).
Step 3: The alkoxide ion then facilitates the movement of electrons, causing the double bond in the enol to shift and form a new bond with the proton that was abstracted. This results in the formation of a ketone structure.
Step 4: The ketone is stabilized due to the strong resonance stabilization of the carbonyl group, making the isomerization thermodynamically favorable.
Step 5: The reaction is reversible, but the equilibrium strongly favors the ketone form over the enol form due to the greater stability of the carbonyl compound.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Vinyl Alcohols
Vinyl alcohols are a class of compounds characterized by the presence of a hydroxyl group (-OH) attached to a carbon-carbon double bond (C=C). They are typically unstable due to their tendency to tautomerize, which means they can readily convert to more stable forms, such as carbonyl compounds (aldehydes or ketones). This instability is a key factor in understanding their reactivity and the mechanisms involved in their isomerization.
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03:51
Vinyl alcohols yield tautomers.
Tautomerization
Tautomerization is a chemical reaction that involves the rearrangement of atoms in a compound, resulting in the interconversion between two isomeric forms, typically involving a shift of a hydrogen atom and a change in the position of a double bond. In the case of vinyl alcohols, tautomerization leads to the formation of carbonyl compounds, which are generally more stable. Understanding this process is crucial for proposing mechanisms for the isomerization of vinyl alcohols.
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Mechanisms of Isomerization
The mechanisms of isomerization describe the step-by-step pathways through which one isomer transforms into another. For vinyl alcohols, this often involves proton transfer, bond breaking, and bond formation, leading to the conversion into carbonyl compounds. Familiarity with reaction mechanisms, including the role of catalysts and intermediates, is essential for accurately proposing and understanding the isomerization processes involved.
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Related Practice
Textbook Question
Compound A (C7H11Br) is treated with magnesium in ether to give B (C7H11MgBr), which reacts violently with D2O to give 1-methylcyclohexene with a deuterium atom on the methyl group (C). Reaction of B with acetone (CH3COCH3) followed by hydrolysis gives D (C10H18O). Heating D with concentrated H2SO4 gives E (C10H16), which decolorizes two equivalents of Br2 to give F (C10H16Br4). E undergoes hydrogenation with excess H2 and a Pt catalyst to give isobutylcyclohexane. Determine the structures of compounds A through F, and show your reasoning throughout.
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Textbook Question
Vinyl alcohols are generally unstable, quickly isomerizing to carbonyl compounds. Propose mechanisms for the following isomerizations.
(a)
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Textbook Question
Grignard reagents react slowly with oxetane to produce primary alcohols. Propose a mechanism for this reaction, and suggest why oxetane reacts with Grignard reagents even though most ethers do not.
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Textbook Question
Geminal diols, or 1,1-diols, are usually unstable, spontaneously losing water to give carbonyl compounds. Therefore, geminal diols are regarded as hydrated forms of ketones and aldehydes. Propose a mechanism for the acid-catalyzed loss of water from propane-2,2-diol to give acetone.
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Textbook Question
Vinyl alcohols are generally unstable, quickly isomerizing to carbonyl compounds. Propose mechanisms for the following isomerizations.
(b)
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