Textbook Question
Identify each of the following compounds from its molecular formula and its IR and 1H NMR spectra.
d. C4H8O2
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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 62
The 1H NMR spectra of three isomers with molecular formula C7H14O are shown here. Which isomer produces which spectrum?
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Verified step by step guidance1
Analyze the molecular formula C7H14O. This indicates the presence of one oxygen atom and a degree of unsaturation, which could correspond to a carbonyl group or an ether functional group.
Examine the 1H NMR spectrum provided. The spectrum shows three distinct signals with integration values of 6H, 3H, 2H, and 1H. These integration values correspond to the number of protons contributing to each signal.
Interpret the chemical shifts (PPM values): The signal at approximately 2 PPM suggests protons adjacent to a carbonyl group or an electronegative atom. The signal at 1 PPM corresponds to alkyl protons in a less deshielded environment, likely from methyl groups.
Consider the splitting patterns: The multiplet at 2 PPM (2H) suggests coupling with adjacent protons, indicating a CH2 group. The singlet at 1 PPM (6H) suggests two equivalent methyl groups, likely attached to the same carbon atom.
Match the spectrum to the isomer: Based on the integration, chemical shifts, and splitting patterns, identify the structural features of the isomer that correspond to the observed NMR data. For example, the presence of a tert-butyl group (6H) and a CH2 group (2H) near an oxygen atom or carbonyl group could be indicative of the correct isomer.
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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 (chemical shifts) and their integration (area under the peaks) help identify the types of hydrogen present and their relative quantities.
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Isomerism
Isomerism refers to the phenomenon where compounds have the same molecular formula but different structural or spatial arrangements. In the case of C7H14O, the isomers can differ in the arrangement of carbon chains, functional groups, or stereochemistry. Understanding isomerism is crucial for interpreting NMR spectra, as different isomers will produce distinct patterns of peaks due to variations in their hydrogen environments.
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Integration and Peak Splitting
In 1H NMR, the integration of peaks corresponds to the number of hydrogen atoms contributing to that signal, while peak splitting provides insight into the number of neighboring hydrogen atoms (n+1 rule). For example, a peak integrating to 6 H indicates a group of hydrogens that are likely equivalent, while splitting patterns can suggest the presence of adjacent hydrogen atoms, aiding in the identification of specific isomers.
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Related Practice
Textbook Question
An alkyl halide reacts with an alkoxide ion to form a compound whose 1H NMR spectrum is shown here. Identify the alkyl halide and the alkoxide ion. (Hint: See Section 9.15.)
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Textbook Question
Compound A, with molecular formula C4H9Cl, shows two signals in its 13C NMR spectrum. Compound B, an isomer of compound A, shows four signals, and in the proton-coupled mode, the signal farthest downfield is a doublet. Identify compounds A and B.
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Textbook Question
The 1H NMR spectrum of 2-propen-1-ol is shown here. Indicate the protons in the molecule that are responsible for each of the signals in the spectrum.
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Textbook Question
Would it be better to use 1H NMR or 13C NMR spectroscopy to distinguish 1-butene, cis-2-butene, and 2-methylpropene? Explain your answer.
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Textbook Question
Identify each of the following compounds from its molecular formula and its IR and 1H NMR spectra:
b. C6H12O2
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