Textbook Question
What alkyl halide will be obtained in greatest yield? Ignore stereoisomers.
a.
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Ch. 12 - Radicals
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 13, Problem 38a
What five-carbon alkene forms the same product whether it reacts with HBr in the presence of a peroxide or with HBr in the absence of a peroxide?
Verified step by step guidance1
Identify the key difference between the two reaction conditions: In the presence of a peroxide, the reaction follows the anti-Markovnikov rule (radical mechanism), while in the absence of a peroxide, the reaction follows the Markovnikov rule (ionic mechanism).
Understand that the product will be the same in both cases only if the addition of HBr to the alkene does not create regioisomers. This means the alkene must be symmetrical or structured such that both Markovnikov and anti-Markovnikov additions lead to the same product.
Consider the structure of five-carbon alkenes. A symmetrical alkene, such as 2-pentene, will produce the same product regardless of the reaction pathway because the addition of HBr will occur at equivalent positions on the double bond.
Analyze the mechanism for both conditions: In the absence of a peroxide, the H⁺ adds to the carbon with more hydrogens (Markovnikov rule), and in the presence of a peroxide, the Br• radical adds to the carbon with more hydrogens (anti-Markovnikov rule). For a symmetrical alkene like 2-pentene, both pathways lead to the same product.
Conclude that the five-carbon alkene that forms the same product under both conditions is a symmetrical alkene, such as 2-pentene, because its structure ensures identical outcomes regardless of the reaction mechanism.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Markovnikov's Rule
Markovnikov's Rule states that when HX (where X is a halogen) adds to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This rule helps predict the major product of electrophilic addition reactions, particularly in the absence of peroxides.
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03:54
The 18 and 16 Electron Rule
Anti-Markovnikov Addition
Anti-Markovnikov addition occurs when the addition of HX to an alkene results in the halogen attaching to the less substituted carbon. This is typically facilitated by the presence of peroxides, which lead to a radical mechanism that reverses the regioselectivity observed in standard electrophilic additions.
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02:43Anti-Markovnikov addition of alcohols to terminal alkynes yields aldehydes
Radical Mechanism
A radical mechanism involves the formation of free radicals during a chemical reaction. In the context of alkene reactions with HBr in the presence of peroxides, this mechanism allows for the anti-Markovnikov addition, where the bromine atom attaches to the less substituted carbon, leading to different product outcomes compared to the non-radical pathway.
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03:28The mechanism of Radical Polymerization.
Related Practice
Textbook Question
Draw the structures of four six-carbon alkenes that form the same product, whether they react with HBr in the presence of a peroxide or with HBr in the absence of a peroxide.
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Textbook Question
What alkyl halide will be obtained in greatest yield? Ignore stereoisomers.
b.
1
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Textbook Question
How many monochlorination products would be obtained if all stereoisomers are included?
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Textbook Question
How many monochlorination products can be obtained from the radical chlorination of methylcyclohexane? Disregard stereoisomers.
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Textbook Question
Which product would be obtained in greatest yield? Explain.