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 53b
Match each of the 1H NMR spectra with one of the following compounds:
b. <IMAGE>
Verified step by step guidance1
Step 1: Analyze the chemical shift values (in ppm) on the x-axis of the 1H NMR spectrum. The spectrum ranges from approximately 0 to 3 ppm, which suggests the presence of protons in an aliphatic environment (no aromatic or highly deshielded protons).
Step 2: Examine the integration values provided above each peak. The integration values indicate the relative number of protons contributing to each signal: 1H, 2H, 2H, 6H, and 3H. These values correspond to the number of hydrogens in different chemical environments.
Step 3: Consider the splitting patterns of the peaks. The splitting patterns (multiplets) are caused by spin-spin coupling with neighboring protons. For example, the 1H peak appears as a multiplet, suggesting it is coupled to adjacent protons. Similarly, the 2H peaks are also multiplets, indicating coupling with nearby protons.
Step 4: Match the chemical shift values and integration data to possible functional groups. For instance, the peak at approximately 1 ppm with an integration of 6H likely corresponds to two equivalent methyl groups (-CH3) in a symmetrical environment. The peak at approximately 3 ppm with an integration of 1H may correspond to a proton near an electronegative atom or functional group.
Step 5: Use the integration, chemical shift, and splitting data to deduce the structure of the compound. Compare the spectrum to the provided list of compounds and identify the one whose structure matches the observed NMR data. Ensure that the number of protons and their environments align with the spectrum.
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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.
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1H NMR Integration
Chemical Shift
Chemical shift refers to the position of a peak in an NMR spectrum, which indicates the electronic environment of the hydrogen atoms. Different functional groups and molecular structures influence the chemical shift, causing protons in different environments to resonate at different frequencies. Understanding chemical shifts is crucial for interpreting the spectrum and identifying the types of hydrogen present in a compound.
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Integration and Multiplicity
Integration in 1H NMR refers to the area under each peak, which correlates to the number of hydrogen atoms contributing to that signal. Multiplicity describes the splitting pattern of the peaks, which arises from neighboring hydrogen atoms (n+1 rule). Analyzing both integration and multiplicity helps in deducing the number of hydrogen atoms and their connectivity in the molecular structure.
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Related Practice
Textbook Question
How can 1H NMR distinguish between the compounds in each of the following pairs?
g.
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Textbook Question
Determine the ratios of the chemically nonequivalent protons in a compound if the steps of the integration curves measure 40.5, 27, 13, and 118 mm, from left to right across the spectrum. Draw the structure of a compound whose 1H NMR spectrum would show these integrals in the observed order.
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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
The 1H NMR spectra of three isomers with molecular formula C4H9Br are shown here. Which isomer produces which spectrum?
b. <IMAGE>
2746
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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>
1533
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