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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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 13a
Predict the major products of the following reactions. Include stereochemistry where applicable.
(a) 1−methylcyclohexene + BH3⋅THF then H2O2, OH–
Verified step by step guidance1
Step 1: Recognize the reaction type. The given reaction involves hydroboration-oxidation, which is a two-step process used to convert alkenes into alcohols. This reaction proceeds with anti-Markovnikov addition and syn stereochemistry.
Step 2: Analyze the structure of the starting material. The starting material is 1-methylcyclohexene, which is a cyclic alkene with a methyl group attached to the double bond. The double bond is the reactive site in this reaction.
Step 3: In the first step, BH3⋅THF adds to the alkene. Boron (BH3) adds to the less substituted carbon of the double bond (anti-Markovnikov addition), while hydrogen adds to the more substituted carbon. This step occurs with syn stereochemistry, meaning both boron and hydrogen add to the same face of the double bond.
Step 4: In the second step, the boron is replaced by a hydroxyl group (-OH) through oxidation using H2O2 and OH-. The hydroxyl group retains the same stereochemistry as the boron in the previous step, resulting in syn addition of the -OH and H groups.
Step 5: Predict the major product. The major product will be an alcohol with the hydroxyl group attached to the less substituted carbon of the original double bond. Ensure to include stereochemistry in the product, as the addition is syn.
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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 process used to convert alkenes into alcohols. In the first step, borane (BH3) adds across the double bond of the alkene in a syn addition, resulting in a trialkylborane intermediate. The second step involves oxidation with hydrogen peroxide (H2O2) and hydroxide (OH-), which replaces the boron atom with a hydroxyl group, yielding an alcohol with anti-Markovnikov orientation.
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General properties of hydroboration-oxidation.
Stereochemistry
Stereochemistry refers to the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In reactions involving alkenes, stereochemistry is crucial as it determines the configuration of the resulting products. For example, syn and anti additions can lead to different stereoisomers, which can have distinct physical and chemical properties.
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Markovnikov's Rule
Markovnikov's Rule states that in the addition of HX to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached, while the halide (or other substituent) will attach to the carbon with fewer hydrogen atoms. In the context of hydroboration-oxidation, the reaction proceeds via anti-Markovnikov addition, where the hydroxyl group ends up on the less substituted carbon, which is a key aspect to consider when predicting the major products.
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Related Practice
Textbook Question
Show how you would accomplish the following synthetic conversions.
(b) but-1-ene → butan-2-ol
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Textbook Question
Predict the major products of the following reactions. Include stereochemistry where applicable.
(c)
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1
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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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Textbook Question
Predict the major products of the following reactions. Include stereochemistry where applicable.
(b) trans-4,4-dimethylpent-2-ene + BH3⋅THF then H2O2, OH–
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Textbook Question
When (Z)-3-methylhex-3-ene undergoes hydroboration–oxidation, two isomeric products are formed. Give their structures, and label each asymmetric carbon atom as (R) or (S). What is the relationship between these isomers?
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