Textbook Question
Predict the product(s) of the following nucleophilic aromatic substitution reactions occurring by the benzyne mechanism.
(b)
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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 55
Mullins 1st EditionCh. 23 - Benzene I: Aromatic Stability and Substitution ReactionsProblem 55Chapter 22, Problem 55
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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Identify the starting material as p-chlorotoluene, where the chlorine atom is para to the methyl group on the benzene ring.
Recognize that the benzyne mechanism involves the elimination of a hydrogen atom (Ha) and a leaving group (Cl) to form a triple bond in the benzene ring, creating a benzyne intermediate.
In the first step, NaOH at high temperature deprotonates the hydrogen (Ha) adjacent to the chlorine, forming a carbanion.
The carbanion then expels the chloride ion, resulting in the formation of the benzyne intermediate, characterized by a triple bond between two adjacent carbon atoms in the benzene ring.
The benzyne intermediate can undergo nucleophilic attack at either of the two carbons involved in the triple bond, leading to two possible products after quenching with H3O+.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Benzyne Mechanism
The benzyne mechanism involves the formation of a highly reactive intermediate known as benzyne, which occurs when a hydrogen atom is removed from a benzene ring, typically in the presence of strong bases. This intermediate features a triple bond between two carbon atoms in the aromatic ring, leading to unique reactivity patterns that differ from typical electrophilic aromatic substitution.
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General Mechanism
Proton Abstraction
Proton abstraction is the process of removing a proton (H+) from a molecule, often facilitated by a strong base. In the context of the benzyne mechanism, the proton removed (H_a) is crucial for generating the benzyne intermediate, which then undergoes further reactions to yield final products. Understanding this step is essential for predicting the outcome of the reaction.
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Product Formation
The formation of products in organic reactions often involves the rearrangement of intermediates and the addition of nucleophiles. In the case of the benzyne mechanism, the benzyne intermediate can react with nucleophiles or undergo further transformations, leading to the formation of two distinct products. Identifying these products requires knowledge of the reaction conditions and the nature of the substituents on the aromatic ring.
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Related Practice
Textbook Question
Predict the products of the following nucleophilic aromatic substitution reactions.
(c)
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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 major product of the following electrophilic aromatic substitution reactions.
(c)
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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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