Textbook Question
Propose a mechanism for the following reaction:
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Ch. 28 - Pericyclic Reactions
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 25, Problem 32
What is the product of the following [1,3] sigmatropic rearrangement, A or B?
![Chemical structure showing a [1,3] sigmatropic rearrangement with products labeled A and B.](https://static.studychannel-dev.pearsondev.tech/courses/organic-chemistry/thumbnails/7d32594d-bf7d-4007-b4a3-ad32290b6c43)
Verified step by step guidance1
Step 1: Understand the concept of a [1,3] sigmatropic rearrangement. This is a pericyclic reaction where a sigma bond migrates along with the simultaneous reorganization of π-electrons. The numbers [1,3] indicate the positions of the atoms involved in the migration.
Step 2: Identify the starting material and locate the sigma bond that will migrate. Look for the bond adjacent to a π-system (such as a double bond or aromatic ring) that can participate in the rearrangement.
Step 3: Analyze the movement of electrons. Use curved arrows to show the breaking of the sigma bond and the formation of a new sigma bond at the [1,3] position. Ensure that the π-electrons are reorganized to maintain the stability of the system.
Step 4: Predict the product structure. After the rearrangement, verify the connectivity of the atoms and ensure that the new sigma bond is formed at the correct position. Compare the resulting structure to options A and B.
Step 5: Evaluate the stability of the products (A and B) if necessary. Consider factors such as resonance stabilization, steric hindrance, and electronic effects to determine which product is more likely to form.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
[1,3] Sigmatropic Rearrangement
[1,3] sigmatropic rearrangement is a type of pericyclic reaction where a sigma bond and a pi bond undergo a concerted rearrangement. In this process, a group migrates from one atom to another within a molecule, typically involving a shift of atoms or groups across a conjugated system. Understanding the mechanism and the stereochemistry involved is crucial for predicting the product of such reactions.
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Nomenclature of Sigmatropic Shifts
Conjugation
Conjugation refers to the overlap of p-orbitals across adjacent double bonds or lone pairs, leading to increased stability and delocalization of electrons. In the context of sigmatropic rearrangements, conjugation plays a significant role in stabilizing the transition state and influencing the regioselectivity of the reaction. Recognizing the conjugated systems involved helps in determining the favored product.
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Regioselectivity
Regioselectivity is the preference of a chemical reaction to yield one structural isomer over others when multiple possibilities exist. In [1,3] sigmatropic rearrangements, the orientation of the migrating group can lead to different products, A or B. Analyzing the stability of the resulting isomers and the reaction conditions can help predict which product will be favored.
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Related Practice
Textbook Question
Draw the product of each of the following reactions:
e.
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Textbook Question
If the compounds shown here are heated, one will form one product from a [1,3] sigmatropic rearrangement and the other will form two products from two different [1,3] sigmatropic rearrangements. Draw the products of the reactions.
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Textbook Question
Draw the product of each of the following reactions:
d.
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Textbook Question
Draw the product formed when each of the following compounds undergoes an electrocyclic reaction
b. under photochemical conditions.
1.
2.
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Textbook Question
Draw the product of each of the following sigmatropic rearrangements:
c.
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