Textbook Question
Predict the major products of the following reactions.
(c) 2-methylpent-2-ene + BH3⋅THF
(d) the product from part (c) + H2O2/OH−
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Ch.8 - Reactions of Alkenes
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 8, Problem 11b
Show how you would accomplish the following synthetic conversions.
(b) but-1-ene → butan-2-ol
Verified step by step guidance1
Identify the functional group transformation: The conversion is from an alkene (but-1-ene) to a secondary alcohol (butan-2-ol). This suggests a hydration reaction where water is added across the double bond.
Choose the appropriate reaction conditions: To achieve Markovnikov addition (where the OH group attaches to the more substituted carbon), use an acid-catalyzed hydration reaction. This typically involves using dilute sulfuric acid (H₂SO₄) and water.
Write the reaction mechanism: The mechanism involves three steps: (1) Protonation of the double bond by H⁺ (from H₂SO₄) to form a carbocation intermediate, (2) Nucleophilic attack by water (H₂O) on the carbocation, and (3) Deprotonation of the oxonium ion to form the alcohol.
Consider regioselectivity: The Markovnikov rule ensures that the OH group attaches to the more substituted carbon (C-2 in but-1-ene), resulting in butan-2-ol as the major product.
Verify stereochemistry: Since the reaction forms a secondary alcohol, the product may exist as a racemic mixture of enantiomers if the carbon atom bearing the OH group becomes a chiral center.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydroboration-Oxidation
Hydroboration-oxidation is a two-step reaction used to convert alkenes into alcohols. In the first step, an alkene reacts with diborane (B2H6) to form an organoborane intermediate. This intermediate is then oxidized in the second step using hydrogen peroxide (H2O2) and a base, resulting in the formation of an alcohol. This method is particularly useful for converting alkenes to alcohols with anti-Markovnikov selectivity.
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General properties of hydroboration-oxidation.
Markovnikov's Rule
Markovnikov's Rule states that when HX (where X is a halogen or hydroxyl group) adds to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This principle helps predict the outcome of electrophilic addition reactions, guiding the formation of more stable carbocation intermediates during the reaction process, which is crucial for understanding the synthesis of butan-2-ol from but-1-ene.
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Rearrangement Reactions
Rearrangement reactions involve the structural reorganization of a molecule to form a more stable product. In the context of converting but-1-ene to butan-2-ol, understanding how carbocation rearrangements can occur is essential. For example, during the addition of water to an alkene, the formation of a more stable secondary carbocation can lead to the desired alcohol product, emphasizing the importance of stability in reaction pathways.
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Related Practice
Textbook Question
Predict the major products of the following reactions.
a. propene + BH3⋅THF
b. the product from part (a) + H2O2/OH−
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Textbook Question
Show how you would accomplish the following synthetic conversions.
c. 2-bromo-2,4-dimethylpentane → 2,4-dimethylpentan-3-ol
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Textbook Question
Show how you would accomplish the following synthetic conversions.
a. but-1-ene → butan-1-ol
1628
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Textbook Question
Predict the major products of the following reactions. Include stereochemistry where applicable.
(a) 1−methylcyclohexene + BH3⋅THF then H2O2, OH–
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Textbook Question
In the hydroboration of 1-methylcyclopentene shown in Solved Problem 8-3, the reagents are achiral, and the products are chiral. The product is a racemic mixture of trans-2-methylcyclopentanol, but only one enantiomer is shown. Show how the other enantiomer is formed.
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