Textbook Question
For the molecules shown, give the number of signals expected and the relative ratio of the signal integrations.
(b)
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Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
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Mullins 1st EditionCh. 15 - Structural Identification II: Nuclear Magnetic Resonance SpectroscopyProblem 16
Mullins 1st EditionCh. 15 - Structural Identification II: Nuclear Magnetic Resonance SpectroscopyProblem 16Chapter 14, Problem 16
How many sets of equivalent hydrogens are present in the molecule that resulted in this NMR spectrum? [Recall that some signals can be split into multiple peaks—they are still just one signal.]
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Identify the molecular structure of the compound in question. This is crucial as the arrangement of atoms will determine the equivalence of hydrogen atoms.
Examine the symmetry of the molecule. Symmetrical molecules often have sets of equivalent hydrogens due to their identical chemical environments.
Look for groups of hydrogens that are in the same chemical environment. Hydrogens in the same environment will produce the same NMR signal.
Consider the presence of any functional groups or substituents that might affect the chemical environment of the hydrogens, leading to different sets of equivalent hydrogens.
Count the distinct sets of equivalent hydrogens based on the analysis of the chemical environments. Each set corresponds to a unique signal in the NMR spectrum, regardless of splitting patterns.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Equivalent Hydrogens
Equivalent hydrogens in a molecule are those that are in identical chemical environments, leading them to produce the same signal in an NMR spectrum. These hydrogens are indistinguishable by NMR and contribute to the same peak or set of peaks. Identifying equivalent hydrogens is crucial for interpreting NMR spectra and understanding molecular symmetry.
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Chemical Shift
Chemical shift refers to the position of an NMR signal along the spectrum, measured in parts per million (ppm). It provides information about the electronic environment surrounding the nuclei, influenced by factors such as electronegativity and hybridization. Understanding chemical shifts helps in identifying the types of hydrogens present and their relative positions in the molecule.
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Spin-Spin Splitting
Spin-spin splitting occurs when non-equivalent hydrogens on adjacent atoms influence each other's magnetic environments, causing a single NMR signal to split into multiple peaks. The number of peaks follows the n+1 rule, where n is the number of neighboring hydrogens. Recognizing splitting patterns aids in determining the connectivity and arrangement of atoms within a molecule.
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Related Practice
Textbook Question
If rotation is restricted, as in the case of the molecule shown, the hydrogens labeled a and b are nonequivalent. Why?
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Textbook Question
How many unique ¹H NMR signals would you expect in an NMR spectrum for the following molecules?
(c)
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Textbook Question
Without worrying about the relative location of the signals (i.e., the chemical shift) or the splitting patterns, draw a spectrum of the following molecule. Be sure to label each signal based on the set of equivalent hydrogens to which it corresponds.
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Textbook Question
How many unique ¹H NMR signals would you expect in an NMR spectrum for the following molecules?
(a)
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Textbook Question
How many unique ¹H NMR signals would you expect in an NMR spectrum for the following molecules?
(b)
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