Textbook Question
Explain why [1,3] sigmatropic migrations of hydrogen cannot occur under thermal conditions, but [1,3] sigmatropic migrations of carbon can.
1
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 14
Why was a deuterated compound used in the last reaction on the preceding page?
Verified step by step guidance1
The reaction shown involves a thermal rearrangement of a cyclic compound. The use of a deuterated compound (CD2) is significant because deuterium (D) is an isotope of hydrogen and can be tracked during the reaction due to its distinct mass and spectroscopic properties.
Deuterium is used to study reaction mechanisms. In this case, it helps to determine whether the hydrogen atoms are retained in their original positions or if they migrate during the rearrangement process.
The arrows in the starting material indicate the movement of electrons during the reaction. This suggests a pericyclic reaction mechanism, likely a [1,5]-sigmatropic shift, where the hydrogen or deuterium migrates across the molecule.
By using deuterium, researchers can confirm the migration pathway and ensure that the observed product matches the expected mechanism. The presence of CD2H in the product indicates that one deuterium atom has migrated while the other remains in its original position.
This experimental design provides evidence for the reaction mechanism and validates theoretical predictions about the behavior of hydrogen and deuterium in pericyclic reactions.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Deuterated Compounds
Deuterated compounds are molecules in which one or more hydrogen atoms are replaced with deuterium, a stable isotope of hydrogen. This substitution can affect the physical and chemical properties of the compound, such as its reactivity and stability. In reactions, deuterated compounds can serve as tracers to study reaction mechanisms or to determine the position of hydrogen atoms in the product.
Recommended video:
Guided course
01:40
Defining meso compounds.
Sigmatropic Rearrangement
Sigmatropic rearrangements are a class of pericyclic reactions where a sigma bond and a pi bond undergo a concerted rearrangement. These reactions often involve the migration of a substituent across a conjugated system, leading to the formation of new bonds. The use of deuterated compounds in these reactions can help elucidate the mechanism by tracking the movement of deuterium during the rearrangement.
Recommended video:
Guided course
03:20Nomenclature of Sigmatropic Shifts
Reaction Mechanism Analysis
Analyzing reaction mechanisms involves understanding the step-by-step process by which reactants transform into products. This includes identifying intermediates, transition states, and the role of catalysts or solvents. In the context of using deuterated compounds, mechanistic studies can reveal how the presence of deuterium influences the reaction pathway and the stability of intermediates, providing insights into the fundamental principles of organic chemistry.
Recommended video:
Guided course
07:48General Mechanism:
Related Practice
Textbook Question
b. Using arrows, show the electron rearrangement that takes place in each reaction.
1.
2.
5
views
Textbook Question
If the terminal sp2 carbon of the substituent attached to the benzene ring is labeled with 14C, where will the label be in the product?
3
views
Textbook Question
b. Using arrows, show the electron rearrangement that takes place in each reaction.
4.
1
views
Textbook Question
Show how 5-methyl-1,3-cyclopentadiene rearranges to form 1-methyl-1,3-cyclopentadiene and 2-methyl-1,3-cyclopentadiene.
Textbook Question
Account for the difference in the products obtained under photochemical and thermal conditions:
1
views