Textbook Question
How many signals would you expect to see in the 1H NMR spectrum of each of the following compounds?
a. CH3CH2CH2CH3
b. BrCH2CH2Br
3
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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 2b
What strength magnetic field is required when a 500-MHz instrument is used for 1H NMR?
Verified step by step guidance1
Understand the relationship between the magnetic field strength (B₀) and the resonance frequency (ν) in NMR spectroscopy. The equation is given by: ν = (γ * B₀) / (2π), where γ is the gyromagnetic ratio for the nucleus being studied (for 1H, γ = 2.675 x 10^8 rad T⁻¹ s⁻¹).
Rearrange the equation to solve for the magnetic field strength (B₀): B₀ = (2π * ν) / γ.
Substitute the given resonance frequency (ν = 500 MHz = 500 x 10^6 Hz) into the equation. Ensure the units are consistent.
Use the gyromagnetic ratio for 1H (γ = 2.675 x 10^8 rad T⁻¹ s⁻¹) in the equation.
Perform the calculation to determine the magnetic field strength (B₀) in Tesla (T).
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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)
Nuclear Magnetic Resonance (NMR) is a powerful analytical technique used to determine the structure of organic compounds. It relies on the magnetic properties of certain nuclei, such as hydrogen-1 (1H), which resonate at specific frequencies when placed in a magnetic field. The frequency of the resonance is directly related to the strength of the magnetic field applied, allowing chemists to infer information about molecular structure and dynamics.
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Larmor Frequency
The Larmor frequency is the frequency at which a nucleus precesses in a magnetic field. It is determined by the equation ω = γB, where ω is the angular frequency, γ is the gyromagnetic ratio specific to the nucleus, and B is the magnetic field strength. For 1H NMR, the Larmor frequency is crucial for determining the required magnetic field strength for a given operating frequency, such as 500 MHz.
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Magnetic Field Strength Calculation
To calculate the magnetic field strength required for a specific NMR frequency, one can rearrange the Larmor equation to B = ω/γ. By substituting the frequency (in radians per second) and the gyromagnetic ratio for hydrogen, one can determine the necessary magnetic field strength. This relationship is fundamental in designing NMR instruments and understanding their operational parameters.
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