Textbook Question
Draw the mechanism for the acid-catalyzed pinacol rearrangement of the following diols.
(b)
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Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
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Mullins 1st EditionCh. 13 - Alcohols, Ethers and Related Compounds: Substitution and EliminationProblem 100a(ii)
Mullins 1st EditionCh. 13 - Alcohols, Ethers and Related Compounds: Substitution and EliminationProblem 100a(ii)Chapter 12, Problem 100a(ii)
Draw the mechanism for the acid-catalyzed pinacol rearrangement of the following diols.
(a) 
Verified step by step guidance1
Identify the diol structure given in the problem. Pinacol rearrangement typically involves a 1,2-diol, so ensure you have the correct starting material.
Protonate one of the hydroxyl groups using the acid catalyst. This step increases the leaving group ability of the hydroxyl group by converting it into a better leaving group, such as water.
Once the hydroxyl group is protonated, it can leave as a water molecule, forming a carbocation at the carbon where the hydroxyl group was attached.
Rearrange the carbocation to form a more stable carbocation. This often involves a 1,2-shift of an alkyl or aryl group adjacent to the carbocation, resulting in a new carbocation at a different position.
Deprotonate the oxonium ion formed after the rearrangement to yield the final ketone product. This step involves the removal of a proton to restore neutrality to the molecule.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Pinacol Rearrangement
Pinacol rearrangement is a chemical reaction where a 1,2-diol undergoes acid-catalyzed dehydration to form a ketone or aldehyde. The reaction involves the migration of an alkyl group and is typically initiated by protonation of one of the hydroxyl groups, leading to the formation of a carbocation intermediate.
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Definition of Claisen Rearrangement
Carbocation Stability
Carbocation stability is crucial in organic reactions, including rearrangements. In pinacol rearrangement, the formation of a stable carbocation intermediate is essential for the migration step. Stability is influenced by factors such as hyperconjugation and resonance, with tertiary carbocations generally being more stable than secondary or primary ones.
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Acid Catalysis
Acid catalysis involves the use of an acid to increase the rate of a chemical reaction. In the pinacol rearrangement, the acid protonates the hydroxyl group, facilitating the formation of a carbocation. This protonation step is critical as it initiates the rearrangement process, allowing the subsequent migration and dehydration steps to occur.
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Related Practice
Textbook Question
Produce a mechanism for the following transformation.
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Textbook Question
Predict the product and draw the mechanism for the acid-catalyzed pinacol rearrangement of the following diols.
(c)
810
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Textbook Question
Predict the product for the acid-catalyzed pinacol rearrangement of the following diols.
(a)
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Textbook Question
Draw a reaction coordinate diagram for the following transformation. Label all product, intermediates, and substrates.
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Textbook Question
Predict the product for the acid-catalyzed pinacol rearrangement of the following diols.
(b)
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