Textbook Question
Sketch the pi molecular orbitals of hexa-1,3,5-triene.
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Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
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Wade 9th EditionCh. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet SpectroscopyProblem 36c
Wade 9th EditionCh. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet SpectroscopyProblem 36cChapter 15, Problem 36c
Show what product would result from the [6 + 2] cycloaddition of hexa-1,3,5-triene with maleic anhydride.
Verified step by step guidance1
Step 1: Recognize that the reaction described is a [6 + 2] cycloaddition. This type of reaction involves the combination of a six-electron π-system (hexa-1,3,5-triene) and a two-electron π-system (maleic anhydride) to form a cyclic product.
Step 2: Analyze the structure of hexa-1,3,5-triene. It contains three conjugated double bonds, which form a six-electron π-system. This makes it suitable for participating in a cycloaddition reaction.
Step 3: Examine the structure of maleic anhydride. It contains a two-electron π-system in its double bond, and the anhydride functional group provides electron-withdrawing properties, making it an excellent dienophile for cycloaddition reactions.
Step 4: Predict the reaction mechanism. The [6 + 2] cycloaddition occurs via a concerted mechanism, where the π-electrons of hexa-1,3,5-triene interact with the π-electrons of maleic anhydride to form a new cyclic structure. The reaction forms two new σ-bonds and a new π-bond in the cyclic product.
Step 5: Draw the product structure. The resulting product will be an eight-membered ring containing the original maleic anhydride functional group and the conjugated system from hexa-1,3,5-triene. Ensure the stereochemistry and connectivity are consistent with the concerted cycloaddition mechanism.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cycloaddition Reactions
Cycloaddition reactions involve the formation of a cyclic compound from two or more reactants. In this case, the [6 + 2] cycloaddition refers to a reaction where a six-membered system (hexa-1,3,5-triene) reacts with a two-component system (maleic anhydride) to form a larger cyclic product. Understanding the mechanism and stereochemistry of cycloaddition is crucial for predicting the structure of the resulting compound.
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Cycloadditions Summary Chart
Hexa-1,3,5-triene
Hexa-1,3,5-triene is a conjugated diene with alternating double bonds, which makes it highly reactive in cycloaddition reactions. Its structure allows for the overlap of p-orbitals during the reaction, facilitating the formation of new sigma bonds. Recognizing the reactivity patterns of such conjugated systems is essential for predicting the outcome of the reaction with maleic anhydride.
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Maleic Anhydride
Maleic anhydride is a cyclic anhydride that acts as a dienophile in Diels-Alder reactions. Its electrophilic nature allows it to react with nucleophilic diene systems like hexa-1,3,5-triene. Understanding the properties of maleic anhydride, including its ability to stabilize the transition state and influence the regioselectivity of the reaction, is vital for determining the final product of the cycloaddition.
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Related Practice
Textbook Question
Show the electronic configuration of the ground state of hexa-1,3,5-triene.
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Textbook Question
Furan and maleimide undergo a Diels–Alder reaction at 25 °C to give the endo isomer of the product. When the reaction takes place at 90 °C, however, the major product is the exo isomer. Further study shows that the endo isomer of the product isomerizes to the exo isomer at 90 °C.
c. Examine your answer to (b) and determine whether this answer applies to a reaction that is kinetically controlled or one that is thermodynamically controlled, or both.
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Textbook Question
Show that the [6 + 2] cyclization of hexa-1,3,5-triene with maleic anhydride is thermally forbidden but photochemically allowed.
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Textbook Question
The pentadienyl radical, H2C=CH–CH=CH–CH2•, has its unpaired electron delocalized over three carbon atoms.
a. Use resonance forms to show which three carbon atoms bear the unpaired electron.
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Textbook Question
Show the Diels–Alder product that would actually result from heating hexa-1,3,5-triene with maleic anhydride.
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