Textbook Question
In the second propagation step in the bromination of toluene, Br2 is only attacked by a radical on the substituent carbon. Why?
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Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring
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. 24 - Benzene II: Reactions Influenced by the Aromatic RingProblem 37
Mullins 1st EditionCh. 24 - Benzene II: Reactions Influenced by the Aromatic RingProblem 37Chapter 23, Problem 37
Oxidation of the phenol shown gives a single quinone product. Predict this product and explain why it is the only one formed.
Verified step by step guidance1
Identify the starting material: The phenol shown in the image is 4-nitrophenol, which has a hydroxyl group (OH) at the para position relative to the nitro group (NO2) on the benzene ring.
Understand the reaction conditions: The reagent used is chromic acid (H2CrO4) in water, which is a strong oxidizing agent commonly used to oxidize phenols to quinones.
Predict the oxidation process: In the oxidation of phenols, the hydroxyl group is converted into a carbonyl group, forming a quinone. The para position of the phenol is typically oxidized to form a para-quinone.
Consider the influence of substituents: The nitro group (NO2) is an electron-withdrawing group, which stabilizes the formation of the quinone by withdrawing electron density from the ring, making the para position more susceptible to oxidation.
Explain the formation of a single product: Due to the electron-withdrawing effect of the nitro group, the para position is the most reactive site for oxidation, leading to the formation of a single para-quinone product, rather than multiple quinone isomers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Phenol Structure and Reactivity
Phenols are aromatic compounds with a hydroxyl (-OH) group attached to a benzene ring. Their structure allows for resonance stabilization, which enhances their reactivity in oxidation reactions. Understanding the specific phenol structure is crucial for predicting the oxidation products, as the position of the hydroxyl group influences the outcome.
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Oxidation Mechanism
Oxidation in organic chemistry typically involves the loss of electrons or an increase in oxidation state. In the case of phenols, oxidation can lead to the formation of quinones, which are cyclic compounds with two carbonyl groups. The mechanism often involves the formation of a radical intermediate, which can stabilize and rearrange to yield a single product, depending on the substituents on the aromatic ring.
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Quinone Formation and Stability
Quinones are highly stable compounds formed from the oxidation of phenols. The stability arises from the delocalization of electrons in the conjugated system of the quinone structure. In cases where a single quinone product is formed, it indicates that the oxidation process leads to a unique arrangement of carbonyl groups that minimizes steric hindrance and maximizes resonance stabilization.
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Related Practice
Textbook Question
Predict the product(s) of the following reactions.
(k)
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Textbook Question
The benzylic bromide shown undergoes neither SN1 nor SN2 substitution reactions. Explain.
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Textbook Question
Suggest the reagents used to effect the transformations shown.
(c)
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Textbook Question
Suggest the reagents used to effect the transformations shown.
(a)
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Textbook Question
When (R)-(1-bromoethyl)benzene is treated with sodium cyanide, a single enantiomer is produced. However, upon treatment of the same molecule with water, a mixture of two enantiomers is obtained.
(a) Explain these results.
(b) Why is only partial racemization sometimes observed?
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