Textbook Question
Draw the product of each of the following reactions:
e.
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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 28b
Draw the product formed when each of the following compounds undergoes an electrocyclic reaction
b. under photochemical conditions.
1. 
2. 
Verified step by step guidance1
Step 1: Identify the type of reaction. The problem specifies an electrocyclic reaction under photochemical conditions. Electrocyclic reactions involve the conversion of a conjugated π-system into a cyclic structure or vice versa, depending on the number of π-electrons and the conditions (thermal or photochemical).
Step 2: Determine the electron count in the conjugated π-system. Both compounds shown are conjugated systems with 6 π-electrons. Under photochemical conditions, the reaction follows the Woodward-Hoffmann rules, which dictate that a 6 π-electron system undergoes a conrotatory ring closure.
Step 3: Apply the conrotatory mechanism. In a conrotatory process, the terminal groups of the conjugated system rotate in opposite directions (one clockwise and the other counterclockwise) to form the cyclic product. This rotation affects the stereochemistry of the substituents attached to the terminal carbons.
Step 4: Analyze the stereochemistry of the substituents. For the first compound, the two CH₃ groups are on opposite sides of the plane of the molecule. After conrotatory closure, the stereochemistry of the product will reflect this initial arrangement. Similarly, for the second compound, the CH₃ groups are on the same side of the plane, which will influence the stereochemistry of the cyclic product.
Step 5: Draw the cyclic product. The final product for each compound will be a cyclohexadiene structure with the substituents positioned according to the conrotatory mechanism and the initial stereochemistry of the reactants. Ensure the stereochemistry is consistent with the rules of the reaction.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electrocyclic Reactions
Electrocyclic reactions are a type of pericyclic reaction where a conjugated system undergoes a cyclic transformation, typically involving the formation or breaking of sigma bonds. These reactions can be influenced by thermal or photochemical conditions, leading to different products. Understanding the mechanism and the stereochemistry involved is crucial for predicting the outcome of these reactions.
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Predicting Electrocyclic Products
Photochemical Conditions
Photochemical conditions refer to reactions that are initiated or driven by light, particularly ultraviolet (UV) light. In electrocyclic reactions, these conditions can alter the stereochemical outcome compared to thermal conditions, often favoring the formation of different isomers. Recognizing how light energy affects molecular orbitals and reaction pathways is essential for predicting products.
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Stereochemistry
Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In electrocyclic reactions, the stereochemical outcome can vary significantly depending on whether the reaction occurs under thermal or photochemical conditions. Understanding concepts like conformation and chirality is vital for accurately drawing and predicting the products of these reactions.
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Related Practice
Textbook Question
What is the product of the following [1,3] sigmatropic rearrangement, A or B?
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Show how the reactant can be converted to the product in two steps.
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Textbook Question
Draw the product of each of the following reactions:
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Show how norbornane can be prepared from cyclopentadiene.
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Textbook Question
a. Name the kind of sigmatropic rearrangement that occurs in each of the following reactions.
1.
2.
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