Textbook Question
cis-3,4-Dimethylcyclobutene undergoes thermal ring opening to form the two products shown. One of the products is formed in 99% yield, the other in 1% yield. Which is which?
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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 37d
Draw the product of each of the following sigmatropic rearrangements:
d. ![Chemical structure illustrating a [5,5] sigmatropic rearrangement with a benzene ring and a carbon chain.](https://static.studychannel.pearsonprd.tech/courses/organic-chemistry/thumbnails/854fe803-2923-471a-8931-7b3cc94bcf04)
Verified step by step guidance1
Identify the type of sigmatropic rearrangement involved. Sigmatropic rearrangements are pericyclic reactions where a sigma bond shifts position along with the reorganization of π-electrons. Common examples include [1,3]- and [1,5]-hydrogen shifts, as well as [3,3]-rearrangements like the Claisen or Cope rearrangements.
Determine the numbering of the atoms involved in the rearrangement. For example, in a [3,3]-sigmatropic rearrangement, there are two sets of three atoms connected by a sigma bond, and the rearrangement involves the migration of this sigma bond while maintaining the connectivity of the π-system.
Draw the starting structure and locate the sigma bond that will migrate. Ensure that the π-system (double bonds or lone pairs) is clearly shown, as it plays a crucial role in the rearrangement.
Apply the rearrangement mechanism. For a [3,3]-sigmatropic rearrangement, break the sigma bond and form a new sigma bond between the terminal atoms of the two three-atom units. Simultaneously, adjust the π-bonds to maintain conjugation and satisfy valency rules.
Draw the product structure, ensuring that all atoms are correctly connected and that the new sigma bond and π-system are properly represented. Verify that the product is consistent with the rules of the sigmatropic rearrangement and that no atoms or electrons are lost in the process.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sigmatropic Rearrangements
Sigmatropic rearrangements are a class of pericyclic reactions where a sigma bond and a pi bond are rearranged in a concerted manner. These reactions typically involve the migration of a substituent across a double bond, resulting in a structural change of the molecule. Understanding the mechanism and the types of sigmatropic rearrangements, such as [1,3] or [3,3] shifts, is crucial for predicting the products formed.
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Nomenclature of Sigmatropic Shifts
Conservation of Orbital Symmetry
Conservation of orbital symmetry is a principle that states that the symmetry of molecular orbitals must be preserved during a reaction. In sigmatropic rearrangements, this principle helps determine whether a reaction is allowed or forbidden based on the symmetry properties of the involved orbitals. Recognizing the symmetry of the reactants and products is essential for predicting the feasibility of the rearrangement.
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Reaction Mechanism
The reaction mechanism describes the step-by-step process by which reactants are converted into products. For sigmatropic rearrangements, understanding the mechanism involves identifying the transition states and intermediates, as well as the role of electron movement. A clear grasp of the mechanism allows chemists to predict the outcome of the rearrangement and the stability of the resulting products.
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Related Practice
Textbook Question
Propose a mechanism for the following reaction:
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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
Explain why two different products are formed from disrotatory ring closure of (2E,4Z,6Z)-octatriene, but only one product is formed from disrotatory ring closure of (2E,4Z,6E)-octatriene.
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Textbook Question
b. What would be the product if trans-2-butene were used instead of ethene?
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Textbook Question
Draw the product of each of the following sigmatropic rearrangements:
c.
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