Textbook Question
In the following allylic radicals, identify the carbon where the new C― Br bond is most likely to form in the second propagation step.
(c)
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Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions
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. 11 - Properties and Synthesis of Alkyl Halides: Radical ReactionsProblem 32d
Mullins 1st EditionCh. 11 - Properties and Synthesis of Alkyl Halides: Radical ReactionsProblem 32dChapter 10, Problem 32d
Predict the products of the following allylic halogenation reactions.
(d) 
Verified step by step guidance1
Identify the allylic position in the given molecule. The allylic position is the carbon atom adjacent to the double bond. In this structure, the allylic position is the carbon atom next to the double bond on the left side.
Understand the role of NBS (N-bromosuccinimide) in the reaction. NBS is used for allylic bromination, which selectively replaces a hydrogen atom at the allylic position with a bromine atom.
Consider the reaction conditions. The presence of light indicates a radical mechanism, which is typical for allylic bromination with NBS.
Generate the allylic radical. The reaction begins with the abstraction of an allylic hydrogen atom by a bromine radical, forming an allylic radical.
Predict the product. The allylic radical will react with a bromine molecule to form the allylic bromide. The bromine atom will attach to the allylic position, resulting in the formation of the allylic brominated product.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Allylic Halogenation
Allylic halogenation is a reaction where a halogen is introduced at the allylic position of an alkene. This position is adjacent to the double bond, allowing for resonance stabilization of the intermediate radical. The reaction typically involves a radical mechanism, initiated by light or heat, and is useful for functionalizing alkenes.
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06:15
The general mechanism of Allylic Halogenation.
N-Bromosuccinimide (NBS)
N-Bromosuccinimide (NBS) is a reagent commonly used for allylic bromination. It provides a controlled source of bromine radicals, which selectively react at the allylic position. NBS is preferred for its ability to minimize over-bromination and its effectiveness in radical reactions, especially under light or heat conditions.
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Radical Mechanism
The radical mechanism involves the formation of radical intermediates, which are highly reactive species with unpaired electrons. In allylic halogenation, radicals are generated by the homolytic cleavage of bonds, often initiated by light. These radicals propagate the reaction by abstracting hydrogen atoms and forming new bonds, leading to the substitution at the allylic position.
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03:28The mechanism of Radical Polymerization.
Related Practice
Textbook Question
The fact that allylic halogenation results in formation of the most stable alkene suggests that it is under thermodynamic control. Thus, the second propagation step must be reversible. Suggest an arrow-pushing mechanism by which the less stable allylic halide might equilibrate to the more stable allylic halide.
Textbook Question
Predict the products of the following allylic halogenation reactions.
(c)
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Textbook Question
(a) Using bond-dissociation energies (Table 5.6), which of the indicated bonds should break most easily?
(b) How does that help you explain the results shown in Figure 11.40?
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Textbook Question
Predict the products of the following allylic halogenation reactions.
(a)
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Textbook Question
The following polyunsaturated fat, which does not exist in nature, is oxidized at a rate similar to oleic acid (Table 11.14), despite having two cis-alkenes. Why?
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