Textbook Question
Vitamin E, especially the B ring and the side chain, is a terpenoid derivative. Identify the isoprene units nature used to make it.
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Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions
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. 11 - Properties and Synthesis of Alkyl Halides: Radical ReactionsProblem 33
Mullins 1st EditionCh. 11 - Properties and Synthesis of Alkyl Halides: Radical ReactionsProblem 33Chapter 10, Problem 33
The fact that allylic halogenation results in formation of the most stable alkene suggests that it is under thermodynamic control. Thus, the second propagation step must be reversible. Suggest an arrow-pushing mechanism by which the less stable allylic halide might equilibrate to the more stable allylic halide.
Verified step by step guidance1
Begin by identifying the allylic halide structure. Allylic halides have a halogen atom attached to a carbon atom that is adjacent to a carbon-carbon double bond.
Recognize that the reaction is under thermodynamic control, meaning the most stable product is favored. This implies that the reaction can equilibrate between different allylic halides.
Consider the mechanism of allylic rearrangement. The key step involves the reversible formation of a π-allyl radical or cation intermediate, which allows for the migration of the halide.
Use arrow-pushing to illustrate the formation of the π-allyl intermediate. Start by showing the homolytic cleavage of the C-X bond, where X is the halogen, to form a radical or cation at the allylic position.
Show the rearrangement of the π-allyl intermediate to form the more stable allylic halide. This involves the movement of the double bond and the reformation of the C-X bond at a different position, resulting in the more stable alkene configuration.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Allylic Halogenation
Allylic halogenation is a reaction where a halogen atom is introduced at the allylic position of an alkene, which is the carbon atom adjacent to a double bond. This reaction often involves radical intermediates and is significant because it can lead to the formation of more stable alkenes through rearrangement or resonance stabilization.
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The general mechanism of Allylic Halogenation.
Thermodynamic Control
Thermodynamic control in a chemical reaction refers to conditions where the product distribution is determined by the relative stability of the products. Under these conditions, the reaction is reversible, and the most stable product predominates, as it is the lowest energy state. This contrasts with kinetic control, where the fastest-forming product is favored.
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Arrow-Pushing Mechanism
Arrow-pushing is a technique used in organic chemistry to illustrate the movement of electrons during chemical reactions. It involves using curved arrows to show how electron pairs move from nucleophiles to electrophiles, helping to visualize the step-by-step process of bond formation and breaking. In the context of allylic halogenation, it helps explain how less stable intermediates can rearrange to form more stable products.
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Related Practice
Textbook Question
Predict the products of the following allylic halogenation reactions.
(c)
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Textbook Question
(a) Using bond-dissociation energies (Table 5.6), which of the indicated bonds should break most easily?
(b) How does that help you explain the results shown in Figure 11.40?
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Textbook Question
Predict the products of the following allylic halogenation reactions.
(d)
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Textbook Question
Predict the products of the following allylic halogenation reactions.
(a)
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Textbook Question
The following polyunsaturated fat, which does not exist in nature, is oxidized at a rate similar to oleic acid (Table 11.14), despite having two cis-alkenes. Why?
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