Textbook Question
Reduction of an alkyne using the Lindlar catalyst, a reaction presented in Section 10.6.2, produces only the cis-alkene. Why?
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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 7d
We have studied a number of pericyclic reactions previously. Draw the mechanism of the steps shown. The section number where this material was first studied is given for your review.
(d) 
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Step 1: Begin by identifying the type of pericyclic reaction involved. Pericyclic reactions include cycloadditions, electrocyclic reactions, sigmatropic rearrangements, and cheletropic reactions. Determine which category the given reaction falls into based on the structural changes in the reactants and products.
Step 2: Analyze the electron movement in the reaction. Pericyclic reactions typically proceed through a concerted mechanism, meaning all bond-making and bond-breaking events occur simultaneously. Use curved arrows to show the flow of electrons during the reaction.
Step 3: Consider the stereochemical implications of the reaction. Pericyclic reactions often follow specific stereochemical rules, such as the Woodward-Hoffmann rules, which depend on the symmetry of the molecular orbitals involved. Determine whether the reaction is thermally or photochemically driven, as this affects the stereochemical outcome.
Step 4: Draw the transition state of the reaction. The transition state is cyclic and involves the overlap of π orbitals. Represent the cyclic structure and the electron movement clearly to illustrate how the reactants transform into the products.
Step 5: Finally, complete the mechanism by showing the final product(s) formed. Ensure that all bonds are correctly represented, and verify that the electron count and stereochemistry align with the rules governing pericyclic reactions.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Pericyclic Reactions
Pericyclic reactions are a class of organic reactions that occur through a concerted mechanism, involving the cyclic rearrangement of electrons. These reactions typically involve the overlap of orbitals in a cyclic transition state, leading to the formation of new bonds without the need for intermediates. Common types include cycloadditions, electrocyclic reactions, and sigmatropic rearrangements, each governed by specific selection rules.
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Properties and Types of Pericyclic Reactions
Mechanism of Reactions
The mechanism of a reaction describes the step-by-step process by which reactants are converted into products. It includes the identification of intermediates, transition states, and the movement of electrons, often illustrated using curved arrows. Understanding the mechanism is crucial for predicting the outcome of reactions and for designing synthetic pathways in organic chemistry.
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Orbital Overlap
Orbital overlap is a fundamental concept in chemistry that refers to the interaction between atomic orbitals when forming chemical bonds. In pericyclic reactions, the overlap of p-orbitals is essential for the concerted movement of electrons, allowing for the formation of new sigma bonds while breaking pi bonds. This concept is key to understanding the stereochemistry and regioselectivity of pericyclic processes.
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Related Practice
Textbook Question
We have studied a number of pericyclic reactions previously. Draw the mechanism of the steps shown. The section number where this material was first studied is given for your review.
(c)
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Textbook Question
We have studied a number of pericyclic reactions previously. Draw the mechanism of the steps shown. The section number where this material was first studied is given for your review.
(a)
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Textbook Question
Diene A participates in a fast and efficient Diels–Alder reaction with maleic anhydride, the powerful dienophile from Assessment 22.9. However, the related diene B does not undergo a Diels–Alder reaction. Why?
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Textbook Question
We have studied a number of pericyclic reactions previously. Draw the mechanism of the steps shown. The section number where this material was first studied is given for your review.
(b)
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Textbook Question
In each Diels–Alder reaction shown, predict the product that will result.
(a)
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