Textbook Question
Allylic halides have the structure
c. Show the products expected from SN1 solvolysis of these halides in ethanol.
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Ch.6 - Alkyl Halides; Nucleophilic Substitution
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 6, Problem 41a
Allylic halides have the structure
a. Show how the first-order ionization of an allylic halide leads to a resonance-stabilized cation.
Verified step by step guidance1
Step 1: Recognize the structure of an allylic halide. The given structure contains a halogen atom (X) attached to a carbon atom that is adjacent to a double bond. This is characteristic of an allylic halide.
Step 2: Understand the first-order ionization process. In this process, the bond between the halogen (X) and the carbon atom breaks heterolytically, resulting in the formation of a carbocation and a halide ion (X⁻).
Step 3: Analyze the resulting carbocation. The carbon atom that loses the halogen becomes positively charged, forming an allylic carbocation. This carbocation is resonance-stabilized due to the delocalization of the positive charge over the π-electron system of the double bond.
Step 4: Draw the resonance structures. The positive charge can shift between the two carbons of the double bond, creating two resonance structures. Use curved arrows to show the movement of electrons from the π-bond to the positively charged carbon.
Step 5: Explain the stabilization. Resonance stabilization occurs because the positive charge is delocalized over multiple atoms, reducing the energy of the carbocation and making it more stable compared to a non-resonance-stabilized carbocation.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Allylic Halides
Allylic halides are organic compounds where a halogen atom is bonded to a carbon atom adjacent to a carbon-carbon double bond. This structure allows for unique reactivity patterns, particularly in nucleophilic substitution reactions, due to the presence of the double bond which can stabilize intermediates formed during reactions.
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First-Order Ionization
First-order ionization refers to a reaction mechanism where a single molecule undergoes a transformation to form an ion, typically involving the departure of a leaving group. In the case of allylic halides, the halogen leaves, generating a carbocation that can be stabilized by resonance with the adjacent double bond.
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Resonance Stabilization
Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. In allylic halides, the carbocation formed after ionization can be stabilized by resonance with the π electrons of the adjacent double bond, leading to a more stable cationic intermediate.
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Related Practice
Textbook Question
Chlorocyclohexane reacts with sodium cyanide (NaCN) in ethanol to give cyanocyclohexane. The rate of formation of cyanocyclohexane increases when a small amount of sodium iodide is added to the solution. Explain this acceleration in the rate.
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Textbook Question
Give the substitution products expected from solvolysis of each compound by heating in ethanol.
(c)
(d)
Textbook Question
Give the substitution products expected from solvolysis of each compound by heating in ethanol.
(a)
(b)
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Textbook Question
Allylic halides have the structure
b. Draw the resonance structures of the allylic cations formed by ionization of the following halides.
(i)
(ii)
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Textbook Question
List the following carbocations in decreasing order of their stability.
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