Textbook Question
b. Are the indicated hydrogens cis or trans?
1.
2
views
Ch. 28 - Pericyclic Reactions
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 25, Problem 8a(2)
a. Identify the mode of ring closure for each of the following electrocyclic reactions
2. 
Verified step by step guidance1
Analyze the given electrocyclic reaction and determine whether it involves a 4n or 4n+2 π-electron system. This is based on the number of π-electrons in the conjugated system undergoing the reaction.
Recall the Woodward-Hoffmann rules for electrocyclic reactions: (1) For a 4n π-electron system, the reaction proceeds via a conrotatory mode under thermal conditions and a disrotatory mode under photochemical conditions. (2) For a 4n+2 π-electron system, the reaction proceeds via a disrotatory mode under thermal conditions and a conrotatory mode under photochemical conditions.
Identify whether the reaction is occurring under thermal or photochemical conditions. This will determine which mode of ring closure (conrotatory or disrotatory) is favored.
Determine the stereochemical outcome of the reaction based on the mode of ring closure. In a conrotatory mode, the terminal substituents rotate in the same direction, while in a disrotatory mode, they rotate in opposite directions.
Apply the above rules to each specific reaction provided in the problem, ensuring to account for the number of π-electrons and the reaction conditions to identify the correct mode of ring closure.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
9mWas this helpful?
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 system undergoes a concerted transformation to form a cyclic compound. These reactions typically involve the breaking and forming of sigma bonds in a cyclic manner, often influenced by thermal or photochemical conditions. Understanding the nature of these reactions is crucial for predicting the products formed during ring closure.
Recommended video:
Guided course
08:11
Predicting Electrocyclic Products
Conjugation and Aromaticity
Conjugation refers to the overlap of p-orbitals across adjacent double bonds, allowing for electron delocalization. This delocalization stabilizes the molecule and is a key factor in determining the reactivity of compounds in electrocyclic reactions. Aromaticity, a special case of conjugation, involves cyclic, planar structures with a specific number of pi electrons, influencing the mode of ring closure in these reactions.
Recommended video:
Guided course
03:27Conjugated states
Woodward-Hoffmann Rules
The Woodward-Hoffmann rules provide a framework for predicting the stereochemistry and outcome of pericyclic reactions, including electrocyclic reactions. These rules are based on the conservation of orbital symmetry and dictate whether a reaction will proceed under thermal or photochemical conditions. Understanding these rules is essential for determining the mode of ring closure in electrocyclic reactions.
Recommended video:
1:18Woodward-Fieser Rules Example 1
Related Practice
Textbook Question
a. Identify the mode of ring closure for each of the following electrocyclic reactions
1.
1
views
Textbook Question
Compare the reaction between 2,4,6-cycloheptatrienone and cyclopentadiene to the reaction between 2,4,6-cycloheptatrienone and ethene. Why does 2,4,6-cycloheptatrienone use two electrons in one reaction and four electrons in the other?
a.
b.
1
views
Textbook Question
Which of the following are correct? Correct any false statements.
b. A conjugated diene with an antisymmetric HOMO undergoes conrotatory ring closure under thermal conditions.
1
views
Textbook Question
b. Are the indicated hydrogens cis or trans?
2.
2
views
Textbook Question
Which of the following are correct? Correct any false statements
c. A conjugated diene with an odd number of double bonds has a symmetric HOMO.
3
views