Textbook Question
Draw the 13C NMR spectrum you would expect to see for each of the molecules shown.
(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 66c
Mullins 1st EditionCh. 15 - Structural Identification II: Nuclear Magnetic Resonance SpectroscopyProblem 66cChapter 14, Problem 66c
For the molecules in Assessment 15.58, give an approximate chemical shift for each indicated carbon. [The range of correct answers is large here.].
(c) 
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Identify the type of carbon atom in the molecule. Determine if it is a primary, secondary, tertiary, or quaternary carbon, as this will influence the chemical shift.
Consider the electronic environment around the carbon atom. Check for any electronegative atoms or groups (like oxygen, nitrogen, or halogens) attached to or near the carbon, as they can deshield the carbon and increase the chemical shift.
Evaluate the hybridization of the carbon atom. For example, sp3 hybridized carbons typically have lower chemical shifts compared to sp2 or sp hybridized carbons.
Take into account any resonance effects. If the carbon is part of a conjugated system or an aromatic ring, this can also affect the chemical shift.
Estimate the chemical shift range based on the above factors. For example, sp3 carbons typically range from 0-50 ppm, sp2 carbons from 100-150 ppm, and sp carbons from 50-100 ppm in a 13C NMR spectrum.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Chemical Shift in NMR Spectroscopy
Chemical shift is a key concept in NMR spectroscopy that refers to the resonant frequency of a nucleus relative to a standard in a magnetic field. It provides information about the electronic environment surrounding a nucleus, typically measured in parts per million (ppm). Factors such as electronegativity of nearby atoms and hybridization state can influence the chemical shift, making it a useful tool for structural analysis.
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1H NMR Chemical Shifts
Factors Affecting Carbon Chemical Shifts
The chemical shift of carbon atoms in NMR is influenced by several factors, including the electronegativity of adjacent atoms, the hybridization of the carbon atom, and the presence of electron-withdrawing or electron-donating groups. For example, carbons bonded to electronegative atoms like oxygen or nitrogen typically show downfield shifts, while those in aliphatic chains are usually upfield.
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Interpreting NMR Spectra
Interpreting NMR spectra involves analyzing the chemical shifts, signal splitting, and integration to deduce the structure of a molecule. Each carbon atom in a molecule can give rise to a distinct signal, and by comparing these shifts to known reference values, one can infer the type of carbon environment present. This process is crucial for identifying functional groups and understanding molecular architecture.
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Related Practice
Textbook Question
Draw the ¹H NMR spectrum you would expect to see for each of the molecules in Assessment 15.63.
(d)
1129
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Textbook Question
Draw the ¹³C NMR spectrum you would expect to see for each of the molecules shown.
(a)
1417
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Textbook Question
Draw the ¹H NMR spectrum you would expect to see for each of the molecules in Assessment 15.63.
(c)
1046
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Textbook Question
For the molecules in Assessment 15.58, give an approximate chemical shift for each indicated carbon. [The range of correct answers is large here.].
(a)
1170
views
Textbook Question
Draw the 13C NMR spectrum you would expect to see for each of the molecules shown.
(c)
1309
views