Textbook Question
Draw a diagram like the one shown in Figure 14.12 to predict
b. the relative intensities of the peaks in a quintet.
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Ch. 14 - NMR Spectroscopy
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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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 15, Problem 22a
Draw a diagram like the one shown in Figure 14.12 to predict
a. the relative intensities of the peaks in a triplet.
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Verified step by step guidance1
Understand the concept of spin-spin splitting: A triplet arises in NMR spectroscopy due to the interaction of a nucleus with two equivalent neighboring nuclei, each having a spin quantum number of 1/2. This results in three peaks with relative intensities determined by the Pascal's triangle (1:2:1).
Recall the rule for peak intensities: The relative intensities of the peaks in a multiplet are determined by the binomial coefficients. For a triplet, the coefficients are derived from the expansion of \((a + b)^2\), which gives 1:2:1.
Draw the diagram: Start by sketching three vertical lines to represent the three peaks of the triplet. Ensure the middle peak is twice as tall as the outer two peaks to reflect the 1:2:1 intensity ratio.
Label the peaks: Indicate the relative intensities of the peaks (1:2:1) below each line. Optionally, you can also label the x-axis as 'Chemical Shift (ppm)' and the y-axis as 'Intensity' to make the diagram more informative.
Verify the splitting pattern: Confirm that the splitting pattern corresponds to the number of equivalent neighboring protons (n = 2) using the \(n + 1\) rule, where \(n\) is the number of equivalent protons. For two equivalent protons, the splitting results in a triplet.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nuclear Magnetic Resonance (NMR) Spectroscopy
NMR spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It relies on the magnetic properties of certain nuclei, primarily hydrogen (1H) and carbon (13C), to provide information about the environment of these atoms in a molecule. The resulting spectra display peaks that correspond to different chemical environments, allowing chemists to infer structural details.
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General NMR Features
Spin-Spin Coupling
Spin-spin coupling, or J-coupling, occurs when the magnetic fields of neighboring nuclei influence each other, leading to the splitting of NMR signals into multiple peaks. This phenomenon is crucial for understanding the multiplicity of signals, such as triplets, which arise from the interaction of a proton with two equivalent neighboring protons. The pattern and intensity of these peaks provide insights into the number of adjacent protons and their arrangement.
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Peak Intensity and Integration
In NMR spectra, the intensity of peaks is proportional to the number of nuclei contributing to that signal. For a triplet, the relative intensities of the peaks follow a specific ratio, typically 1:2:1, reflecting the number of neighboring protons. Understanding peak intensity and integration is essential for quantifying the relative amounts of different hydrogen environments in a molecule, aiding in structural elucidation.
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Related Practice
Textbook Question
How would integration distinguish the 1H NMR spectra of the following compounds?
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Textbook Question
Indicate the number of signals and the multiplicity of each signal in the 1H NMR spectrum of each of the following compounds:
a. CH3CH2CH2CH2CH2CH3
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Textbook Question
Which of the following compounds is responsible for the 1H NMR spectrum shown below?
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Textbook Question
Explain how the following compounds, each with the same molecular formula, could be distinguished by their 1H NMR spectra.
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Textbook Question
Indicate the number of signals and the multiplicity of each signal in the 1H NMR spectrum of each of the following compounds:
c. ClCH2CH2CH2Cl
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