Textbook Question
Vinyl alcohols are generally unstable, quickly isomerizing to carbonyl compounds. Propose mechanisms for the following isomerizations.
(c)
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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 45
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.
Verified step by step guidance1
Step 1: Protonation of one of the hydroxyl groups in propane-2,2-diol occurs under acidic conditions. This increases the electrophilicity of the carbon atom attached to the hydroxyl groups.
Step 2: The protonated hydroxyl group becomes a good leaving group, and water is eliminated, forming a carbocation intermediate at the central carbon atom.
Step 3: A rearrangement occurs where the lone pair of electrons from the remaining hydroxyl group stabilizes the carbocation by forming a double bond between the central carbon and oxygen, resulting in the formation of a carbonyl group.
Step 4: The protonated carbonyl group loses a proton to regenerate the acid catalyst, yielding acetone as the final product.
Step 5: The overall reaction results in the conversion of propane-2,2-diol to acetone with the elimination of water, driven by the stability of the carbonyl group formed.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Geminal Diols
Geminal diols, also known as 1,1-diols, are organic compounds that contain two hydroxyl (-OH) groups attached to the same carbon atom. They are typically unstable and can readily dehydrate to form carbonyl compounds, such as aldehydes or ketones. This transformation is significant in organic chemistry as it illustrates the equilibrium between hydrated forms and their corresponding carbonyl species.
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Acid-Catalyzed Dehydration
Acid-catalyzed dehydration is a chemical reaction where an acid facilitates the removal of water from a compound. In the case of geminal diols, the presence of an acid protonates the hydroxyl group, making it a better leaving group. This process leads to the formation of a carbocation intermediate, which subsequently loses a water molecule to yield a carbonyl compound, such as a ketone or aldehyde.
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Mechanism of Carbonyl Formation
The mechanism of carbonyl formation from geminal diols involves several key steps: protonation of the hydroxyl group, formation of a carbocation, and elimination of water. The carbocation can rearrange or stabilize through resonance, leading to the formation of a stable carbonyl compound. Understanding this mechanism is crucial for predicting the behavior of similar organic compounds and their transformations in various chemical environments.
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Related Practice
Textbook Question
Vinyl alcohols are generally unstable, quickly isomerizing to carbonyl compounds. Propose mechanisms for the following isomerizations.
(a)
7
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Textbook Question
Vinyl alcohols are generally unstable, quickly isomerizing to carbonyl compounds. Propose mechanisms for the following isomerizations.
(b)
1
views
Textbook Question
Show how you would synthesize the following compounds from any starting materials containing no more than six carbon atoms.
(a)
1
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Textbook Question
Show how you would synthesize the following compounds from any starting materials containing no more than six carbon atoms.
(b)
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Textbook Question
Suggest carbonyl compounds and reducing agents that might be used to form the following alcohols.
(e)
(f)
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