Textbook Question
The Eschenmoser–Claisen reaction is a variant of the Claisen reaction studied in this chapter. Based on your answers to Assessments 22.53–22.55, predict a product of this reaction.
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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 60
While not covered explicitly in this chapter, the ene reaction occurs similarly to the Diels–Alder reaction but replaces the electrons from one bond in the diene with the electrons in a C―H bond. Draw the mechanism for the following reaction. [Number the carbons and draw in the hydrogens of the product. And, of course, make a note of bonds formed and bonds broken.]
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Identify the components of the ene reaction: the 'ene' (alkene with an allylic hydrogen) and the 'enophile' (an electron-deficient species). In this case, determine which part of the molecule acts as the ene and which as the enophile.
Number the carbon atoms in the alkene and identify the allylic hydrogen that will participate in the reaction. This hydrogen is typically adjacent to the double bond.
Draw the initial step of the mechanism where the allylic hydrogen is transferred to the enophile. This involves the formation of a new C-H bond and the breaking of the original C-H bond.
Illustrate the movement of electrons: the π electrons from the alkene double bond will form a new σ bond with the enophile, while the electrons from the C-H bond will form a new π bond in the alkene.
Finally, draw the product of the reaction, ensuring that all new bonds are shown, and the numbering of carbons and hydrogens is clear. Highlight the bonds that were formed and those that were broken during the reaction.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Ene Reaction
The ene reaction is a type of pericyclic reaction where an alkene (ene) reacts with a compound containing a hydrogen atom (enophile) to form a new bond. It involves the transfer of electrons from a C-H bond to form a new C-C bond, similar to the Diels–Alder reaction but with different electron sources. Understanding the electron flow and bond formation is crucial for drawing the mechanism.
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Heck Reaction
Pericyclic Reactions
Pericyclic reactions are a class of organic reactions that occur through a concerted process involving cyclic transition states. They are characterized by the redistribution of bonding electrons in a cyclic manner, often without intermediates. Familiarity with these reactions helps in understanding the mechanism of the ene reaction, as they share similar principles of electron movement and bond formation.
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Mechanism Drawing
Drawing mechanisms involves illustrating the step-by-step process of a chemical reaction, showing how reactants transform into products. It requires identifying bonds broken and formed, numbering atoms for clarity, and indicating electron movement. This skill is essential for visualizing the ene reaction, ensuring accurate representation of the molecular changes and understanding the reaction pathway.
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09:36Drawing the E2 Mechanism.
Related Practice
Textbook Question
The product of the Stille coupling reaction (A) tautomerizes in a basic solution to give compound B. B spontaneously converts to C.
(c) Suggest a mechanism for the conversion of B to C
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Textbook Question
In Chapter 20, we studied the aldol reaction. Although not discussed at the time, this reaction is stereospecific, proceeding through the Zimmerman–Traxler transition state shown here.
(a) Show an arrow-pushing mechanism for this concerted reaction.
(b) Why is this a favorable mechanism?
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Textbook Question
The product of the Stille coupling reaction (A) tautomerizes in a basic solution to give compound B. B spontaneously converts to C. (a) Propose a structure for A. (b) Suggest a mechanism for the conversion of A to B.
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Textbook Question
The Johnson–Claisen reaction is a variant of the Claisen reaction studied in this chapter. (a) Suggest a mechanism for the first step. (b) Predict the product (B) that would result from heating intermediate A.
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