Domanda del libro di testo
The 1H NMR spectra of three isomers with molecular formula C7H14O are shown here. Which isomer produces which spectrum?
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Ch. 14 - NMR Spectroscopy
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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TOC.tableOfContents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding31
- 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
Capitolo 14, Problema 57
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.
Guida verificata passo dopo passo1
Analyze the molecular formula C4H9Cl: This indicates that the compound contains 4 carbons, 9 hydrogens, and 1 chlorine atom. The presence of chlorine suggests the compound is an alkyl halide.
Interpret the 13C NMR data for Compound A: The fact that Compound A shows only two signals in its 13C NMR spectrum implies that it has symmetry, reducing the number of unique carbon environments to two.
Interpret the 13C NMR data for Compound B: Compound B, being an isomer of Compound A, also has the formula C4H9Cl. However, it shows four signals in its 13C NMR spectrum, indicating that all four carbons are in unique environments, meaning it lacks symmetry.
Analyze the proton-coupled 13C NMR data for Compound B: The signal farthest downfield being a doublet suggests that one of the carbons is directly bonded to a single hydrogen atom. This is characteristic of a carbon attached to a chlorine atom (due to the electronegativity of chlorine causing deshielding) and having one hydrogen.
Propose structures for A and B: Based on the symmetry and NMR data, Compound A is likely a symmetrical alkyl chloride, such as tert-butyl chloride (2-chloro-2-methylpropane), which has two unique carbon environments. Compound B, with four unique carbon environments and a downfield doublet, is likely 1-chlorobutane, where the carbon bonded to chlorine has one hydrogen and is deshielded.
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NMR Spectroscopy
Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It provides information about the number of unique carbon environments in a molecule, as indicated by the number of signals in the 13C NMR spectrum. The position and splitting of these signals can reveal details about the molecular structure, including functional groups and connectivity.
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General NMR Features
Isomerism
Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations. In this case, compound A and compound B are isomers of each other, meaning they share the same formula (C4H9Cl) but differ in their connectivity or arrangement of atoms, leading to distinct NMR spectral characteristics.
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Signal Splitting in NMR
In NMR spectroscopy, signal splitting occurs due to the interaction between neighboring hydrogen atoms, known as spin-spin coupling. This results in the appearance of multiple peaks for a single signal, which can provide insight into the number of adjacent protons. For example, a doublet indicates that a proton is coupled to one neighboring proton, which is crucial for deducing the structure of compound B in the given question.
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04:35General Assumption for 1H NMR Signals
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Identify the compound with molecular formula C7H14O that gives the following proton-coupled 13C NMR spectrum:
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