Textbook Question
b. Are the indicated hydrogens cis or trans?
1.
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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 11
Will a concerted reaction take place between 1,3-butadiene and 2-cyclohexenone in the presence of ultraviolet light?
Verified step by step guidance1
Identify the type of reaction: The problem involves 1,3-butadiene and 2-cyclohexenone, which suggests a potential pericyclic reaction. Since ultraviolet (UV) light is mentioned, this indicates the possibility of a photochemical reaction, such as a [2+2] cycloaddition.
Understand the reaction conditions: In the presence of UV light, pericyclic reactions follow the photochemical selection rules. These rules are based on the Woodward-Hoffmann principles, which determine whether a reaction is allowed under thermal or photochemical conditions.
Analyze the molecular orbitals: For a [2+2] cycloaddition to occur, the reaction must involve the interaction of the HOMO (highest occupied molecular orbital) of one molecule with the LUMO (lowest unoccupied molecular orbital) of the other. Under photochemical conditions, the electronic excitation alters the orbital symmetry, making the reaction symmetry-allowed.
Determine the feasibility of the reaction: 1,3-butadiene has a conjugated π-system, and 2-cyclohexenone contains a double bond in a cyclic structure. Under UV light, the π-electrons in these molecules can be excited, allowing the reaction to proceed via a concerted mechanism. This makes the [2+2] cycloaddition between these two molecules feasible.
Conclude the reaction type: Based on the analysis, a concerted [2+2] cycloaddition reaction is likely to occur between 1,3-butadiene and 2-cyclohexenone in the presence of UV light, as it satisfies the photochemical selection rules.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Concerted Reactions
Concerted reactions are chemical processes where bond breaking and bond forming occur simultaneously in a single step, without intermediates. This mechanism is crucial in understanding how certain reactions proceed, particularly in systems with multiple reactive sites. The stereochemistry and regioselectivity of the products are often determined by the concerted nature of the reaction.
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07:37
Properties and Types of Pericyclic Reactions
Diels-Alder Reaction
The Diels-Alder reaction is a specific type of concerted reaction involving a diene and a dienophile, leading to the formation of a six-membered ring. In this context, 1,3-butadiene acts as the diene, while 2-cyclohexenone serves as the dienophile. This reaction is thermally allowed and can be influenced by light, making it relevant to the question of ultraviolet light's effect.
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04:02Diels-Alder Retrosynthesis
Ultraviolet Light in Organic Reactions
Ultraviolet (UV) light can provide the energy necessary to promote certain organic reactions, particularly those involving excited states or radical mechanisms. In the context of the question, UV light may facilitate the Diels-Alder reaction by promoting the diene or dienophile to a reactive state, potentially altering the reaction pathway or rate. Understanding the role of UV light is essential for predicting the feasibility of the reaction.
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Related Practice
Textbook Question
Compare the reaction between 2,4,6-cycloheptatrienone and cyclopentadiene to the reaction between 2,4,6-cycloheptatrienone and ethene. Why does 2,4,6-cycloheptatrienone use two electrons in one reaction and four electrons in the other?
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Textbook Question
Explain why maleic anhydride reacts rapidly with 1,3-butadiene but does not react at all with ethene under thermal conditions.
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Textbook Question
a. Name the kind of sigmatropic rearrangement that occurs in each of the following reactions.
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Textbook Question
a. Name the kind of sigmatropic rearrangement that occurs in each of the following reactions.
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Textbook Question
b. Using arrows, show the electron rearrangement that takes place in each reaction.
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