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 13a
In each Diels–Alder reaction shown, predict the product that will result.
(a) 
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Identify the diene and the dienophile in the reaction. In this case, the diene is the compound with two conjugated double bonds, and the dienophile is the compound with the carbonyl groups.
Recognize that the Diels–Alder reaction is a [4+2] cycloaddition, where the diene contributes four π-electrons and the dienophile contributes two π-electrons to form a six-membered ring.
Consider the stereochemistry of the reaction. The Diels–Alder reaction is stereospecific, meaning that the stereochemistry of the dienophile is preserved in the product. If the dienophile is cis, the substituents will be on the same side in the product.
Analyze the regiochemistry of the reaction. The electron-withdrawing groups on the dienophile will direct the reaction to form the most stable product, often resulting in endo selectivity, where substituents are oriented towards the larger bridge in the bicyclic system.
Draw the product by forming a new six-membered ring between the diene and dienophile, ensuring that the stereochemistry and regiochemistry are correctly represented. The product will be a bicyclic compound with the newly formed ring and the original substituents from the dienophile.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Diels-Alder Reaction
The Diels-Alder reaction is a [4+2] cycloaddition reaction between a conjugated diene and a dienophile, forming a six-membered ring. It is a pericyclic reaction that proceeds through a concerted mechanism, meaning bonds are formed and broken simultaneously. This reaction is stereospecific, often preserving the stereochemistry of the reactants in the product.
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Stereochemistry in Diels-Alder Reactions
Stereochemistry plays a crucial role in Diels-Alder reactions, as the configuration of the diene and dienophile affects the stereochemistry of the product. The reaction can produce endo or exo products, with the endo product typically favored due to secondary orbital interactions. The orientation of substituents in the reactants influences the stereochemical outcome of the reaction.
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Endo and Exo Selectivity
Endo and exo selectivity refers to the preference for forming one stereoisomer over another in Diels-Alder reactions. The endo product is favored when the substituents on the dienophile are oriented towards the diene's π system, allowing for stabilizing interactions. This preference is often explained by the endo rule, which suggests that secondary orbital interactions stabilize the transition state leading to the endo product.
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Related Practice
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
In each Diels–Alder reaction shown, predict the product that will result.
(c)
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Textbook Question
Assuming the diene approaches the dienophile from the top, predict the product of the following Diels–Alder reactions.
(c)
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Textbook Question
Figure 22.16(a) <IMAGE> shows a unique example where the Diels–Alder reaction gives a single product (no enantiomers) regardless of whether the diene attacks the dienophile from the top or bottom.
(a) Show the product of the diene attacking from the bottom and confirm that the same product is obtained.
(b) What is special about this product that makes this true?
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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.
(d)
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