Textbook Question
Diazomethane can be used to convert a carboxylic acid to a methyl ester. Propose a mechanism for this reaction.
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Ch. 18 - Reactions of Benzene and Substituted Benzenes
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 19, Problem 33
In the mechanism for electrophilic aromatic substitution with a diazonium ion as the electrophile, why does nucleophilic attack occur on the terminal nitrogen of the diazonium ion rather than on the nitrogen that has the formal positive charge?
Verified step by step guidance1
Understand the structure of the diazonium ion: A diazonium ion has the general structure R-N≡N⁺, where the nitrogen with the formal positive charge is directly bonded to the aromatic ring (R), and the terminal nitrogen is triple-bonded to it.
Recognize the electrophilic nature of the diazonium ion: The diazonium ion is an electrophile because the positive charge on the nitrogen makes the molecule electron-deficient, and it seeks electrons from a nucleophile (in this case, the aromatic ring).
Analyze the electron density distribution: The triple bond between the two nitrogens in the diazonium ion is highly polarized. The terminal nitrogen is more electron-deficient because it is directly bonded to the positively charged nitrogen, which pulls electron density away from it. This makes the terminal nitrogen the most electrophilic site.
Consider steric and electronic factors: The nitrogen with the formal positive charge is directly bonded to the aromatic ring, which creates steric hindrance and reduces its accessibility for nucleophilic attack. Additionally, the terminal nitrogen is more accessible for the nucleophile.
Conclude why the terminal nitrogen is attacked: The nucleophilic aromatic ring attacks the terminal nitrogen because it is the most electrophilic site due to electron deficiency and is sterically more accessible compared to the nitrogen with the formal positive charge.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electrophilic Aromatic Substitution (EAS)
Electrophilic Aromatic Substitution is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This process involves the formation of a sigma complex, where the aromaticity of the ring is temporarily lost. Understanding EAS is crucial for analyzing how different electrophiles, such as diazonium ions, interact with aromatic compounds.
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Diazonium Ion Structure
Diazonium ions are a class of electrophiles characterized by a positively charged nitrogen atom bonded to a nitrogen double bond (N≡N). The terminal nitrogen, which is not positively charged, is more nucleophilic due to its ability to donate electrons. Recognizing the structure and reactivity of diazonium ions helps explain why nucleophilic attack occurs preferentially at the terminal nitrogen.
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Nucleophilicity and Electrophilicity
Nucleophilicity refers to the ability of a species to donate an electron pair, while electrophilicity is the ability to accept an electron pair. In the context of the diazonium ion, the terminal nitrogen is more nucleophilic than the positively charged nitrogen, making it a more favorable site for nucleophilic attack. Understanding these concepts is essential for predicting the outcomes of reactions involving electrophiles and nucleophiles.
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Related Practice
Textbook Question
What product is formed from the reaction of p-methylphenol with benzenediazonium chloride?
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Textbook Question
Draw the structure of the activated benzene ring and the diazonium ion used in the synthesis of each of the following compounds, whose structures can be found on page 607.
b. methyl orange
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Textbook Question
Show how the following compounds can be synthesized from benzene:
d. m-methylnitrobenzene
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Textbook Question
Which amide bond is hydrolyzed in the first step of the conversion of temozolomide to methyldiazonium?
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Textbook Question
Explain why a diazonium group on a benzene ring cannot be used to direct an incoming substituent to the meta position.
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