Textbook Question
Assign each signal in the ¹³C NMR spectra to the molecule shown.
(a) <IMAGE>
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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 54b
Mullins 1st EditionCh. 15 - Structural Identification II: Nuclear Magnetic Resonance SpectroscopyProblem 54bChapter 14, Problem 54b
Draw the expected results of a DEPT sequence for the molecules shown.
(b) 
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Identify the carbon atoms in the molecule and classify them based on the number of hydrogen atoms attached. In DEPT (Distortionless Enhancement by Polarization Transfer) NMR, carbon atoms are classified as CH3, CH2, CH, or quaternary (C with no hydrogens).
Understand the DEPT sequence: DEPT-90 shows only CH groups, DEPT-135 shows CH and CH3 as positive peaks and CH2 as negative peaks, while quaternary carbons do not appear in any DEPT spectrum.
Analyze the molecular structure to determine the type of each carbon atom. Count the number of hydrogens attached to each carbon to classify them as CH3, CH2, CH, or quaternary.
Draw the DEPT-90 spectrum, indicating only the CH groups. These will appear as positive peaks.
Draw the DEPT-135 spectrum, indicating CH and CH3 groups as positive peaks and CH2 groups as negative peaks. Quaternary carbons will not appear in this spectrum.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
DEPT NMR Spectroscopy
Distortionless Enhancement by Polarization Transfer (DEPT) is a technique in NMR spectroscopy used to determine the number of hydrogen atoms attached to carbon atoms in a molecule. It differentiates between CH, CH2, and CH3 groups by using different pulse sequences, providing a clearer understanding of the molecular structure.
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10:06
General NMR Features
Carbon-13 NMR
Carbon-13 NMR is a type of nuclear magnetic resonance spectroscopy that focuses on the carbon-13 isotope. It provides information about the carbon skeleton of organic compounds, helping to identify the number and types of carbon environments in a molecule. This technique is crucial for structural elucidation in organic chemistry.
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04:0013C NMR General Features
Chemical Shift
Chemical shift in NMR spectroscopy refers to the resonant frequency of a nucleus relative to a standard in a magnetic field. It provides insights into the electronic environment surrounding the nucleus, influenced by factors like electronegativity and hybridization. Understanding chemical shifts is essential for interpreting NMR spectra and identifying functional groups.
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Related Practice
Textbook Question
Assign each signal in the ¹³C NMR spectra to the molecule shown.
(b) <IMAGE>
1
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Textbook Question
How many distinct signals would you expect to see in the ¹H NMR spectrum of the following molecules? [Ignore diastereotopic hydrogens for the sake of this assessment.]
(a)
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Textbook Question
How many distinct signals would you expect to see in the ¹H NMR spectrum of the following molecules? [Ignore diastereotopic hydrogens for the sake of this assessment.]
(b)
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Textbook Question
Draw the expected results of a DEPT sequence for the molecules shown.
(a)
Textbook Question
With information from the ¹H NMR and the ¹³C DEPT spectra, structure elucidation becomes even easier. Provide the structure that corresponds to the following data. [The identity of the carbons comes from the DEPT experiment.]
C₆H₁₁BrO₂
IR: 1745 cm ⁻¹
¹H NMR: δ 1.25 (t, 3H), 2.18 (quint, 2H), 2.58 (t, 2H), 3.46 (t, 2H), 4.15 (q, 2H)
¹³C NMR: δ 14.2 (CH₃) , 27.8 (CH₂) , 32.5 (CH₂) , 32.6 (CH₂) , 60.5 (CH₂) , 172.4 (C)
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