Textbook Question
Which of the following compounds reacts with HBr more rapidly?
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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 61
Describe two ways to prepare anisole from benzene.
Verified step by step guidance1
Step 1: **Preparation via Friedel-Crafts Alkylation and Williamson Ether Synthesis**: Start with benzene. Perform a Friedel-Crafts alkylation reaction by reacting benzene with methyl chloride (CH₃Cl) in the presence of a Lewis acid catalyst like AlCl₃. This will yield toluene (methylbenzene). Next, oxidize the methyl group of toluene to a phenol group using an oxidizing agent like KMnO₄. Finally, perform a Williamson Ether Synthesis by reacting phenol with methyl iodide (CH₃I) in the presence of a strong base like NaOH to form anisole (methoxybenzene).
Step 2: **Preparation via Phenol Methylation**: Start with benzene and perform a nitration reaction by reacting benzene with a mixture of concentrated HNO₃ and H₂SO₄ to form nitrobenzene. Reduce nitrobenzene to aniline (aminobenzene) using a reducing agent like Sn/HCl. Convert aniline to phenol by diazotization (using NaNO₂ and HCl at 0-5°C) followed by hydrolysis. Finally, methylate phenol by reacting it with dimethyl sulfate ((CH₃O)₂SO₂) or methyl iodide (CH₃I) in the presence of a base like NaOH to form anisole.
Step 3: **Key Reaction Mechanisms**: In the Friedel-Crafts alkylation, the Lewis acid catalyst (AlCl₃) generates a highly reactive electrophile (CH₃⁺) that reacts with benzene to form toluene. In the Williamson Ether Synthesis, the phenoxide ion (generated by deprotonating phenol with NaOH) acts as a nucleophile and attacks the methyl iodide (CH₃I) to form anisole.
Step 4: **Alternative Reagents and Conditions**: For the phenol methylation step, dimethyl sulfate ((CH₃O)₂SO₂) can also be used as a methylating agent instead of methyl iodide. Additionally, other oxidizing agents like CrO₃ or PCC can be used to oxidize toluene to phenol.
Step 5: **Safety and Environmental Considerations**: Ensure proper handling of reagents like AlCl₃, H₂SO₄, and dimethyl sulfate, as they are highly reactive and hazardous. Use appropriate safety equipment and dispose of waste according to environmental regulations.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
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 the case of preparing anisole from benzene, EAS can occur through the introduction of a methoxy group (-OCH3) via the reaction of benzene with an electrophile such as methyl iodide in the presence of a strong base, which generates the necessary electrophile.
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EAS Review
Friedel-Crafts Alkylation
Friedel-Crafts alkylation is a specific type of electrophilic aromatic substitution that involves the addition of an alkyl group to an aromatic ring. To prepare anisole, benzene can react with an alkyl halide (like methyl chloride) in the presence of a Lewis acid catalyst (such as AlCl3), which facilitates the formation of the alkyl cation that subsequently attaches to the benzene ring, forming an alkylated product that can be further converted to anisole.
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Methoxy Group Introduction
The methoxy group (-OCH3) is a common functional group in organic chemistry that can be introduced into aromatic compounds through various methods. In the context of preparing anisole, the methoxy group can be introduced via the reaction of benzene with dimethyl sulfate or methyl iodide in the presence of a base, leading to the formation of anisole. Understanding the reactivity and stability of the methoxy group is crucial for predicting the outcomes of these reactions.
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Related Practice
Textbook Question
Why is anisole nitrated more rapidly than thioanisole under the same conditions?
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Textbook Question
For each of the following compounds, indicate the ring carbon(s) that is/are nitrated when the compound is treated with HNO3/H2SO4:
e.
f.
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Textbook Question
Show two pairs of reagents that would each result in formation of the following compound:
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Textbook Question
An aromatic hydrocarbon with a molecular formula of C13H20 has an 1H NMR spectrum with a signal at ~7 ppm that integrates to 5H. It also has two singlets; one of the singlets has 1.5 times the area of the second. What is the structure of the aromatic hydrocarbon?
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Textbook Question
Show how the following compounds can be synthesized from benzene:
a. N,N,N-trimethylanilinium iodide
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