Textbook Question
What are the products of the following reactions?
a.
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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 68b
A mixture of 0.10 mol benzene and 0.10 mol p-xylene was allowed to react with 0.10 mol nitronium ion until all the nitronium ion was gone. Two products were obtained: 0.002 mol of one and 0.098 mol of the other.
b. Why was more of one product obtained than of the other?
Verified step by step guidance1
Step 1: Understand the reaction. The nitronium ion (NO₂⁺) is an electrophile that reacts with benzene and p-xylene in an electrophilic aromatic substitution reaction. Benzene and p-xylene are the reactants, and the products are nitrobenzene and nitro-p-xylene, respectively.
Step 2: Analyze the reactivity of benzene and p-xylene. Benzene is less reactive toward electrophilic aromatic substitution because it lacks electron-donating groups. In contrast, p-xylene has two methyl groups, which are electron-donating and activate the aromatic ring, making it more reactive toward the nitronium ion.
Step 3: Consider the regioselectivity of the reaction. The methyl groups on p-xylene direct the nitronium ion to the ortho and para positions due to their electron-donating inductive and hyperconjugative effects. This increases the likelihood of nitro-p-xylene formation compared to nitrobenzene.
Step 4: Relate the product distribution to the reactivity. Since p-xylene is more reactive than benzene, it reacts preferentially with the nitronium ion. This explains why a larger amount of nitro-p-xylene (0.098 mol) was formed compared to nitrobenzene (0.002 mol).
Step 5: Conclude the reasoning. The difference in product amounts is due to the higher reactivity of p-xylene, which is activated by its methyl groups, compared to benzene, which lacks activating substituents. This leads to a preferential reaction of the nitronium ion with p-xylene.
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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 this case, the nitronium ion acts as the electrophile, attacking the benzene and p-xylene. The reactivity of the aromatic compounds and the stability of the resulting intermediates influence the distribution of products formed.
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Substituent Effects on Reactivity
The presence of substituents on an aromatic ring can significantly affect its reactivity towards electrophiles. In the case of p-xylene, which has two methyl groups, these groups are electron-donating and activate the ring towards further substitution. This results in a higher likelihood of forming one product over the other, depending on the position of substitution and the stability of the intermediates.
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Product Distribution and Kinetics
The distribution of products in a reaction can be influenced by both thermodynamic and kinetic factors. In this scenario, the formation of one product over the other may be due to the stability of the transition states or intermediates involved in the reaction. The more stable product is often formed in greater quantities, reflecting the reaction's pathway and the relative energies of the products.
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Related Practice
Textbook Question
Use the four compounds shown below to answer the following questions:
b. Why is o-fluorobenzoic acid the weakest of the ortho-halo-substituted benzoic acids?
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Textbook Question
b. Rank the same esters from most reactive to least reactive in the second slow step of a nucleophilic acyl substitution reaction (collapse of the tetrahedral intermediate).
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Textbook Question
a. Rank the following esters from most reactive to least reactive in the first slow step of a nucleophilic acyl substitution reaction (formation of the tetrahedral intermediate):
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Textbook Question
What are the products of the following reactions?
a.
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Textbook Question
Does m-xylene or p-xylene react more rapidly with Cl2 + FeCl3? Explain your answer.
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