Textbook Question
Predict the product of the following benzylic bromination reactions.
(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 63b
Mullins 1st EditionCh. 11 - Properties and Synthesis of Alkyl Halides: Radical ReactionsProblem 63bChapter 10, Problem 63b
Predict the product of the following benzylic bromination reactions.
(b) 
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Identify the type of reaction: This is a benzylic bromination reaction, which typically involves the substitution of a hydrogen atom at the benzylic position with a bromine atom.
Locate the benzylic position: The benzylic position is the carbon atom directly attached to the benzene ring. In this reaction, identify the carbon atom that is adjacent to the benzene ring.
Consider the mechanism: Benzylic bromination usually proceeds via a radical mechanism. The presence of a radical initiator, such as N-bromosuccinimide (NBS), facilitates the formation of a benzylic radical.
Predict the formation of the benzylic radical: The hydrogen atom at the benzylic position is abstracted, forming a benzylic radical. This radical is stabilized by resonance with the benzene ring.
Determine the final product: The benzylic radical reacts with bromine to form the brominated product. The bromine atom replaces the hydrogen atom at the benzylic position, resulting in the formation of the benzylic bromide.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Benzylic Bromination
Benzylic bromination is a type of radical halogenation reaction where a bromine atom is introduced at the benzylic position, which is the carbon atom directly attached to a benzene ring. This reaction typically involves the use of N-bromosuccinimide (NBS) and a radical initiator, such as light or heat, to generate bromine radicals that selectively react with the benzylic hydrogen atoms.
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Mechanism of Allylic Bromination.
Radical Mechanism
Radical mechanisms involve the formation and reaction of radicals, which are species with unpaired electrons. In benzylic bromination, the reaction proceeds through a radical chain mechanism, starting with the generation of bromine radicals, followed by hydrogen abstraction from the benzylic position, and finally, the formation of the brominated product. Understanding the stability and reactivity of radicals is crucial for predicting the outcome of such reactions.
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Benzylic Position Stability
The benzylic position is highly reactive due to the stability of the benzylic radical formed during the reaction. This stability arises from resonance, where the unpaired electron can be delocalized over the aromatic ring, making the benzylic radical more stable than other alkyl radicals. This enhanced stability is a key factor in the selectivity of benzylic bromination reactions, as it favors the formation of products at the benzylic position.
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Related Practice
Textbook Question
A halogenation intended to make compound A formed B instead.
(c) Given the two mechanisms you drew, why might B have formed selectively?
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Textbook Question
The human body can excrete drugs and other exogenous molecules by converting them into polar, water-soluble compounds by a reaction similar to the autoxidation described in Section 11.6. Why are the following drug candidate molecules susceptible to oxidation by this pathway?
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Textbook Question
A halogenation intended to make compound A formed B instead.
(d) Without looking it up, would you expect C–Ha or C–Hb to have the lower bond-dissociation energy?
Textbook Question
Predict the product of the following benzylic bromination reactions.
(a)
1
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