Textbook Question
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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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 15c
Mullins 1st EditionCh. 15 - Structural Identification II: Nuclear Magnetic Resonance SpectroscopyProblem 15cChapter 14, Problem 15c
How many unique ¹H NMR signals would you expect in an NMR spectrum for the following molecules?
(c) 
Verified step by step guidance1
Identify the molecule in question. Understanding the structure is crucial for predicting the number of unique ¹H NMR signals.
Examine the symmetry of the molecule. Symmetrical molecules often have fewer unique signals because equivalent hydrogens produce the same signal.
Determine the different types of hydrogen environments present in the molecule. Hydrogens in different chemical environments will produce distinct signals.
Consider the presence of chiral centers or stereochemistry, as these can affect the equivalence of hydrogen atoms and thus the number of signals.
Count the number of unique hydrogen environments. Each unique environment corresponds to a unique ¹H NMR signal.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
¹H NMR Spectroscopy
¹H NMR (Proton Nuclear Magnetic Resonance) spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic environment of hydrogen atoms. Each unique hydrogen environment in a molecule produces a distinct signal in the NMR spectrum, allowing chemists to deduce the number and types of hydrogen atoms present.
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General NMR Features
Chemical Equivalence
Chemical equivalence in NMR refers to hydrogen atoms that are in identical environments and thus produce the same NMR signal. Identifying chemically equivalent protons is crucial for predicting the number of unique signals in a spectrum. Protons are equivalent if they can be interchanged by a symmetry operation, such as rotation or reflection, without altering the molecule's structure.
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Symmetry in Molecules
Symmetry in molecules plays a significant role in determining the number of unique NMR signals. Symmetrical molecules often have fewer unique signals because equivalent protons are indistinguishable in the NMR spectrum. Recognizing symmetry elements, such as planes of symmetry or axes of rotation, helps in identifying equivalent hydrogen atoms and predicting the NMR pattern.
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Related Practice
Textbook Question
How many sets of equivalent hydrogens are in each molecule shown?
(c)
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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
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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