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)
1
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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 31a
Mullins 1st EditionCh. 11 - Properties and Synthesis of Alkyl Halides: Radical ReactionsProblem 31aChapter 10, Problem 31a
In the following allylic radicals, identify the carbon where the new C–Br bond is most likely to form in the second propagation step.
(a) 
Verified step by step guidance1
Identify the structure of the allylic radical. The image shows two resonance structures of an allylic radical, where the unpaired electron is delocalized over the allylic position.
Understand the concept of resonance. Resonance in organic chemistry refers to the delocalization of electrons across adjacent atoms, which stabilizes the molecule. In allylic radicals, the unpaired electron can be shared between the two carbon atoms adjacent to the double bond.
Determine the most stable position for the new bond formation. In the case of allylic radicals, the new bond is most likely to form at the carbon atom where the radical is most stable due to resonance stabilization.
Consider the electronic effects. The formation of the C–Br bond will occur at the carbon atom that can best stabilize the positive charge that results from the radical's electron pairing with the bromine atom.
Select the carbon atom for bond formation. Based on resonance structures, the new C–Br bond is most likely to form at the carbon atom that is part of the more stable resonance structure, which is typically the less substituted carbon in the allylic position.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Allylic Radical Stability
Allylic radicals are stabilized by resonance, where the unpaired electron is delocalized over adjacent pi bonds. This delocalization increases the stability of the radical, making allylic positions favorable sites for reactions. Understanding this stability is crucial for predicting where new bonds will form in radical reactions.
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03:43
The radical stability trend.
Resonance Structures
Resonance structures depict the delocalization of electrons within a molecule, showing different possible configurations. In the case of allylic radicals, resonance allows the radical to be distributed over multiple carbon atoms, influencing the site of bond formation. Recognizing resonance structures helps in identifying the most reactive sites in a molecule.
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Radical Propagation Steps
Radical propagation involves the transfer of an unpaired electron to form new bonds, typically in a chain reaction. In the second propagation step, the radical reacts with another molecule, such as Br2, to form a new C–Br bond. Understanding the mechanism of propagation steps is essential for predicting the outcome of radical reactions.
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Related Practice
Textbook Question
In the following molecules, identify the carbon where the radical is most likely to form in the first propagation step.
(c)
2
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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.
(b)
2
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Textbook Question
In the following molecules, identify the carbon where the radical is most likely to form in the first propagation step.
(d)
1
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Textbook Question
Predict the products of the following allylic halogenation reactions.
(a)
2
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Textbook Question
In the following reaction, which C―H bond would be most likely to react with a bromine radical?