Textbook Question
The 1H NMR spectra of three isomers with molecular formula C4H9Br are shown here. Which isomer produces which spectrum?
c. <IMAGE>
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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 54b
The 1H NMR spectra of three isomers with molecular formula C4H9Br are shown here. Which isomer produces which spectrum?
b. <IMAGE>
Verified step by step guidance1
Analyze the molecular formula C4H9Br, which indicates the presence of four carbons, nine hydrogens, and one bromine atom. This suggests the possibility of structural isomers such as 1-bromobutane, 2-bromobutane, and 2-methyl-2-bromopropane.
Examine the 1H NMR spectrum provided. Note the chemical shift values (in ppm), the splitting patterns (multiplets, doublets, singlets, etc.), and the relative integration of the peaks, which correspond to the number of protons in each environment.
Identify the peak near 3-4 ppm, which is characteristic of protons attached to a carbon bonded to a bromine atom. This region helps distinguish the position of the bromine in the molecule.
Look at the splitting patterns and chemical shifts of the peaks in the 0-2 ppm region. These peaks correspond to alkyl protons and provide information about the branching and connectivity of the carbon chain.
Match the observed spectrum to the expected NMR patterns for each isomer. For example, 1-bromobutane will show a triplet for the CH3 group, a multiplet for the CH2 groups, and a distinct peak for the CH2-Br group. Similarly, 2-bromobutane and 2-methyl-2-bromopropane will have unique splitting patterns and chemical shifts based on their structures.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
1H NMR Spectroscopy
Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It provides information about the number of hydrogen atoms in different environments within a molecule, indicated by peaks in the spectrum. The position of these peaks, measured in parts per million (PPM), reflects the electronic environment surrounding the hydrogen atoms, allowing chemists to infer structural details.
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1H NMR Integration
Chemical Shifts
Chemical shifts in 1H NMR spectra refer to the specific PPM values at which the peaks appear, influenced by the electronic environment of the hydrogen atoms. Different functional groups and molecular structures cause variations in these shifts, helping to identify the presence of specific groups such as alkyl, aromatic, or halogenated carbons. Understanding chemical shifts is crucial for interpreting the spectrum and correlating it with the corresponding isomer.
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Integration of Peaks
The integration of peaks in a 1H NMR spectrum indicates the relative number of hydrogen atoms contributing to each signal. The area under each peak is proportional to the number of protons in that environment, allowing for the determination of the ratio of different types of hydrogen in the molecule. This information is essential for distinguishing between isomers, as it helps to confirm the molecular structure based on the integration values.
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Related Practice
Textbook Question
Answer the following questions:
c. What is the relationship between coupling constant in hertz and operating frequency?
d. How does the operating frequency in NMR spectroscopy compare with the operating frequency in IR and UV/Vis spectroscopy?
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Textbook Question
Identify each of the following compounds from the 1H NMR data and molecular formula:
c. C5H10O2: a 3H triplet at 1.15 ppm
a 3H triplet at 1.25 ppm
a 2H quartet at 2.33 ppm
a 2H quartet at 4.13 ppm
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Textbook Question
Identify each of the following compounds from the 1H NMR data and molecular formula:
b. C8H9Br: a 3H doublet at 2.01 ppm a 1H quartet at 5.14 ppm
a 5H broad singlet at 7.35 ppm
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Textbook Question
The 1H NMR spectra of three isomers with molecular formula C4H9Br are shown here. Which isomer produces which spectrum?
a. <IMAGE>
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Textbook Question
Match each of the 1H NMR spectra with one of the following compounds:
b. <IMAGE>
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