Textbook Question
Show how the following compounds can be prepared from benzene:
c.
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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 88a
Propose a mechanism for each of the following reactions:
a. 
Verified step by step guidance1
Step 1: Analyze the starting material and product. The starting material contains a methoxy-substituted aromatic ring and a diketone structure. The product is a fused bicyclic compound with a ketone and an aromatic ring. This suggests a mechanism involving cyclization and aromatic stabilization.
Step 2: Protonation of the carbonyl group. In the presence of HCl, the carbonyl oxygen of one of the ketones is protonated, increasing its electrophilicity and making the adjacent carbon more susceptible to nucleophilic attack.
Step 3: Intramolecular nucleophilic attack. The aromatic ring, activated by the methoxy group, acts as a nucleophile. The electron-rich aromatic ring attacks the electrophilic carbon of the protonated carbonyl group, forming a new C-C bond and initiating cyclization.
Step 4: Rearrangement and loss of water. After cyclization, a rearrangement occurs to stabilize the intermediate. This may involve the loss of a water molecule (dehydration) to form the final conjugated bicyclic structure.
Step 5: Deprotonation and aromatic stabilization. The final step involves deprotonation to restore aromaticity in the ring system, yielding the stable bicyclic ketone product.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Elimination Reactions
Elimination reactions involve the removal of atoms or groups from a molecule, resulting in the formation of a double bond or a ring structure. In this context, the reaction with HCl suggests that a proton (H+) is likely being added to one part of the molecule while a leaving group departs, leading to the formation of a more stable product. Understanding the mechanism of elimination is crucial for predicting the outcome of the reaction.
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Recognizing Elimination Reactions.
Mechanism of Electrophilic Aromatic Substitution
Electrophilic aromatic substitution (EAS) is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In this case, HCl can act as an electrophile, and the presence of electron-donating groups, like methoxy (–OCH3), can influence the reactivity and orientation of the substitution. Recognizing how substituents affect the mechanism is essential for proposing accurate reaction pathways.
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Resonance and Stability
Resonance refers to the delocalization of electrons in a molecule, which can stabilize certain structures. In the context of the provided reaction, the stability of the intermediates formed during the elimination process can significantly affect the reaction pathway. Understanding how resonance contributes to the stability of intermediates helps in predicting the favored products of the reaction.
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Related Practice
Textbook Question
The pKa values of a few ortho-, meta-, and para-substituted benzoic acids are shown below:
The relative pKa values depend on the substituent. For chloro-substituted benzoic acids, the ortho isomer is the most acidic and the para isomer is the least acidic; for nitro-substituted benzoic acids, the ortho isomer is the most acidic and the meta isomer is the least acidic; and for amino-substituted benzoic acids, the meta isomer is the most acidic and the ortho isomer is the least acidic. Explain these relative acidities.
c. NH2: meta > para > ortho
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Textbook Question
Identify A–J:
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Textbook Question
Propose a mechanism for each of the following reactions:
b.
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Textbook Question
When heated with chromic acid, compound A forms benzoic acid. Identify compound A from its 1H NMR spectrum.
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Textbook Question
The pKa values of a few ortho-, meta-, and para-substituted benzoic acids are shown below:
The relative pKa values depend on the substituent. For chloro-substituted benzoic acids, the ortho isomer is the most acidic and the para isomer is the least acidic; for nitro-substituted benzoic acids, the ortho isomer is the most acidic and the meta isomer is the least acidic; and for amino-substituted benzoic acids, the meta isomer is the most acidic and the ortho isomer is the least acidic.
Explain these relative acidities.
a. Cl: ortho > meta > para
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