Textbook Question
For each compound, predict the major product of free-radical bromination. Remember that bromination is highly selective, and only the most stable radical will be formed.
(a) cyclohexane
(b) methylcyclopentane
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Ch.4 - The Study of Chemical Reactions
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 4, Problem 45c,d
Draw the important resonance forms of the following free radicals.
(c) 
(d) 
Verified step by step guidance1
Identify the free radical in the given structure. For CH3COO⋅, the radical is on the oxygen atom. For the cyclohexene radical, the radical is on the carbon atom adjacent to the double bond.
For CH3COO⋅, consider the resonance between the radical on the oxygen and the carbonyl group. The lone electron on the oxygen can form a double bond with the carbon, while the π bond of the carbonyl group can shift to the oxygen, creating a new radical site.
Draw the resonance structure for CH3COO⋅: Move the lone electron from the oxygen to form a double bond with the carbon, and move the π bond electrons of the carbonyl group to the oxygen, resulting in a structure with a radical on the carbonyl oxygen.
For the cyclohexene radical, consider the resonance involving the π bond. The radical electron can pair with one of the π electrons, forming a new π bond, while the other π electron moves to the adjacent carbon, creating a new radical site.
Draw the resonance structure for the cyclohexene radical: Shift the radical electron to form a double bond with the adjacent carbon, and move one of the π electrons to the next carbon, resulting in a new radical site on the carbon adjacent to the original double bond.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Resonance Structures
Resonance structures are different ways of drawing the same molecule that illustrate the delocalization of electrons. They help in understanding the stability and reactivity of molecules, particularly in cases where a single Lewis structure cannot adequately represent the electron distribution. In free radicals, resonance can stabilize the unpaired electron by allowing it to be shared across multiple atoms.
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Drawing Resonance Structures
Free Radicals
Free radicals are species that contain an unpaired electron, making them highly reactive. They can be formed through various processes, including the breaking of covalent bonds. Understanding the nature of free radicals is crucial for predicting their behavior in chemical reactions, as they often seek to pair their unpaired electron by reacting with other molecules.
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03:28The mechanism of Radical Polymerization.
Stability of Radicals
The stability of free radicals is influenced by their structure and the presence of substituents. Generally, radicals are more stable when they are tertiary (attached to three other carbon atoms) compared to secondary or primary radicals. This stability can be explained by hyperconjugation and resonance effects, which help to delocalize the unpaired electron, reducing the overall energy of the radical.
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Related Practice
Textbook Question
In the presence of a small amount of bromine, the following light-promoted reaction has been observed.
a. Write a mechanism for this reaction. Your mechanism should explain how both products are formed. (Hint: Notice which H atom has been lost in both products.)
Textbook Question
Draw the important resonance forms of the following free radicals.
a.
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Textbook Question
In the presence of a small amount of bromine, the following light-promoted reaction has been observed.
b. Explain why only this one type of hydrogen atom has been replaced, in preference to any of the other hydrogen atoms in the starting material.
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Textbook Question
Write a mechanism for the light-initiated reaction of cyclohexane with chlorine to give chlorocyclohexane. Label the initiation and propagation steps.
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Textbook Question
Draw the important resonance forms of the following free radicals.
b.
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