Textbook Question
Predict the products of the following nucleophilic aromatic substitution reactions.
(c)
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Ch. 23 - Benzene I: Aromatic Stability and Substitution 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. 23 - Benzene I: Aromatic Stability and Substitution ReactionsProblem 56b
Mullins 1st EditionCh. 23 - Benzene I: Aromatic Stability and Substitution ReactionsProblem 56bChapter 22, Problem 56b
Predict the product(s) of the following nucleophilic aromatic substitution reactions occurring by the benzyne mechanism.
(b) 
Verified step by step guidance1
Identify the substrate and the nucleophile: The substrate is a bromobenzene derivative with a methyl group ortho to the bromine. The nucleophile is methoxide ion (CH₃O⁻) in methanol.
Recognize the reaction conditions: The reaction is carried out at 100°C, which is conducive to the benzyne mechanism, a type of nucleophilic aromatic substitution.
Understand the benzyne mechanism: This mechanism involves the elimination of the leaving group (Br) to form a highly reactive benzyne intermediate. This occurs through the removal of a proton adjacent to the leaving group, forming a triple bond in the benzene ring.
Predict the formation of the benzyne intermediate: The base (NaOCH₃) abstracts a proton from the carbon adjacent to the bromine, resulting in the elimination of bromide ion and formation of the benzyne intermediate.
Determine the product formation: The methoxide ion can attack either carbon of the benzyne intermediate, leading to a mixture of products. The nucleophile adds to the benzyne, restoring aromaticity and forming a methoxy-substituted benzene.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nucleophilic Aromatic Substitution (NAS)
Nucleophilic aromatic substitution is a reaction where a nucleophile replaces a leaving group on an aromatic ring. This process typically occurs when the aromatic compound has electron-withdrawing groups that stabilize the negative charge developed during the reaction. The mechanism can proceed via different pathways, including the benzyne mechanism, which involves the formation of a highly reactive intermediate known as benzyne.
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NAS in the addition-elimination pathway
Benzyne Mechanism
The benzyne mechanism is a specific pathway for nucleophilic aromatic substitution that involves the formation of a benzyne intermediate. This occurs when a leaving group, such as bromine, is eliminated to create a triple bond between two carbon atoms in the aromatic ring. The nucleophile then attacks this highly reactive intermediate, leading to the substitution product. This mechanism is particularly relevant when the aromatic compound lacks strong electron-withdrawing groups.
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Role of Sodium Methoxide and Methanol
Sodium methoxide (NaOCH3) acts as a strong nucleophile in the reaction, while methanol (CH3OH) serves as the solvent. The nucleophile attacks the benzyne intermediate formed during the reaction, facilitating the substitution process. The choice of methanol as a solvent is important as it can stabilize the reaction intermediates and help in the solvation of the nucleophile, enhancing the overall reaction efficiency.
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Related Practice
Textbook Question
Beginning with benzene, synthesize the following substituted benzenes. The ideal number of steps is indicated.
(d)
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Textbook Question
Predict the products of the following reactions.
(a)
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Textbook Question
Predict the products of the following reactions.
(a)
Textbook Question
Conversion of t-butylbenzene to a phenol results in two products when the reaction occurs through the benzyne mechanism. Devise a sequence involving a diazonium ion in which only one phenol product is produced.
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Textbook Question
Assume that Ha is the proton removed in the first step of the benzyne mechanism with p-chlorotoluene. Draw the benzyne intermediate and identify the two products that will result.
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