Textbook Question
Predict the product of the Claisen reactions shown.
(b)
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Ch. 22 - Conjugated Systems II: Pericyclic Reactions
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
Chapter 21, Problem 43b
Predict the product of the following reactions. [When all of the reactions from this chapter are shown together, you must first decide which type of reaction each is. Is it a Diels–Alder, an electrocyclic, or a sigmatropic rearrangement? Drawing the product will be easier once this determination is made.]
(b) 
Verified step by step guidance1
Identify the type of reaction: The given structure is a bicyclic compound with a double bond, and the reaction involves heat (Δ). This suggests a pericyclic reaction, likely an electrocyclic reaction due to the presence of a conjugated system.
Determine the type of electrocyclic reaction: Since the reaction is under thermal conditions, consider whether it is a conrotatory or disrotatory process. For a 4n+2 π-electron system (like a 6 π-electron system), thermal conditions favor a conrotatory closure.
Analyze the stereochemistry: In a conrotatory process, the substituents on the termini of the conjugated system rotate in the same direction. Here, the hydrogen and the bridgehead carbon will rotate conrotatorily.
Predict the product structure: The conrotatory rotation will result in the formation of a new sigma bond between the termini of the conjugated system, leading to a new ring closure. The stereochemistry of the substituents will be determined by the direction of rotation.
Draw the final product: The product will be a new bicyclic compound with a different ring junction, reflecting the conrotatory closure of the original double bond. Ensure the stereochemistry is consistent with the conrotatory mechanism.
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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 pi-electron system undergoes a cyclic reorganization to form a new sigma bond. These reactions can be either thermal or photochemical, with the stereochemistry of the product being determined by the Woodward-Hoffmann rules. In thermal electrocyclic reactions, the stereochemistry is governed by conrotatory or disrotatory motion, depending on the number of pi electrons involved.
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08:11
Predicting Electrocyclic Products
Woodward-Hoffmann Rules
The Woodward-Hoffmann rules are a set of principles used to predict the stereochemistry of pericyclic reactions, including electrocyclic reactions. These rules state that the stereochemical outcome of a reaction is determined by the conservation of orbital symmetry. For thermal reactions, systems with 4n pi electrons undergo conrotatory closure, while those with 4n+2 pi electrons undergo disrotatory closure, affecting the stereochemistry of the product.
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1:18Woodward-Fieser Rules Example 1
Conrotatory and Disrotatory Motion
In electrocyclic reactions, conrotatory and disrotatory motions describe the way in which the ends of the pi system rotate to form a new sigma bond. Conrotatory motion involves the ends rotating in the same direction, while disrotatory motion involves them rotating in opposite directions. The type of motion affects the stereochemistry of the product, with conrotatory leading to one stereochemical outcome and disrotatory leading to another, as dictated by the number of pi electrons and reaction conditions.
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05:51Two Steps to Predicting Any Electrocyclic Products
Related Practice
Textbook Question
The [2 + 2] cyclization is especially useful when done intramolecularly.
(a) What makes intramolecular reactions more favorable?
(b) Predict the product of the following cyclization (slight modification of a reaction from Angew. Chem. 2011, 50, 5149)
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Textbook Question
Suggest a diene and a dienophile that would give the following products.
(c)
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Textbook Question
Predict the product of the following reactions. [When all of the reactions from this chapter are shown together, you must first decide which type of reaction each is. Is it a Diels–Alder, an electrocyclic, or a sigmatropic rearrangement? Drawing the product will be easier once this determination is made.]
(a)
2
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Textbook Question
Predict the product of the Claisen reactions shown.
(c)
2
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Textbook Question
By forming a Lewis acid–Lewis base complex with the dienophile, Lewis acids are able to increase the rate of Diels–Alder reactions. Why might this be true?
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