Textbook Question
Draw the expected signal for a hydrogen with the following coupling constants.
(a) Hₐ : δ 5.34 (Jₐ꜀ = 12 , Jₐ₆ = 2)
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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 41
Mullins 1st EditionCh. 15 - Structural Identification II: Nuclear Magnetic Resonance SpectroscopyProblem 41Chapter 14, Problem 41
Though it wasn't discussed, what coupling constant would you expect for Hₐ and H꜀ in the spectrum of trans-but-2-enoic acid in Figure 15.50? Justify your answer.
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First, understand the concept of coupling constants in NMR spectroscopy. The coupling constant, denoted as J, is a measure of the interaction between nuclear spins and is expressed in Hertz (Hz). It provides information about the spatial relationship between coupled nuclei.
Identify the structure of trans-but-2-enoic acid. The trans configuration indicates that the substituents on the double bond are on opposite sides. This affects the coupling constant between the hydrogen atoms Hₐ and H꜀.
Consider the geometry of the molecule. In trans-but-2-enoic acid, Hₐ and H꜀ are on opposite sides of the double bond, which typically results in a larger coupling constant compared to a cis configuration due to the dihedral angle between the protons.
Recall typical values for coupling constants in alkenes. For trans alkenes, the coupling constant is usually in the range of 12-18 Hz. This is due to the larger dihedral angle compared to cis alkenes, which have smaller coupling constants (6-12 Hz).
Justify the expected coupling constant for Hₐ and H꜀ in trans-but-2-enoic acid based on the trans configuration and typical values for coupling constants in similar structures. The trans configuration leads to a larger coupling constant due to the spatial arrangement of the protons.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Coupling Constant
The coupling constant, denoted as J, is a measure of the interaction between nuclear spins in NMR spectroscopy. It is expressed in hertz (Hz) and provides information about the spatial relationship between coupled nuclei. The value of J depends on the number of bonds separating the nuclei and the geometry of the molecule, with larger values typically indicating closer or more direct interactions.
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02:54
Sonogashira Coupling Reaction
Trans Configuration
In organic chemistry, a trans configuration refers to the arrangement of substituents across a double bond where they are on opposite sides. This configuration affects the coupling constant, as trans protons typically exhibit larger coupling constants compared to cis protons due to the more extended spatial arrangement, which influences the magnetic interaction between them.
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NMR Spectroscopy
Nuclear Magnetic Resonance (NMR) spectroscopy is a technique used to determine the structure of organic compounds by observing the magnetic properties of atomic nuclei. In NMR, the chemical environment of hydrogen atoms (protons) is analyzed, providing insights into molecular structure, including the number of hydrogen atoms, their connectivity, and interactions, such as coupling constants, which help deduce spatial arrangements.
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Related Practice
Textbook Question
Replace Hₐ, H₆, and H꜀ in methyl benzene with a deuterium. What is the relationship between the three products you obtain? Based on this, how many signals would you expect for these hydrogens in the ¹H NMR spectrum?
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Textbook Question
Replace Hₐ and H₆ in hexane with a deuterium. What is the relationship between the two products you obtain? Based on this, would you expect the two hydrogens to give one or two signals in the ¹H NMR spectrum?
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Textbook Question
Alkene hydrogens usually appear at similar chemical shifts between 5 and 6 ppm. The alkene hydrogens in the structure shown are very different. Rationalize the difference in chemical shifts between Hₐ and H₆ in the structure shown.
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Textbook Question
Replace Hₐ and H₆ in acetone with a deuterium. What is the relationship between the two products you obtain? Based on this, would you expect the two hydrogens to give one or two signals in the ¹H NMR spectrum?
1161
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Textbook Question
Draw the expected signal for a hydrogen with the following coupling constants.
(b) Hₐ : δ 3.34 (Jₐ꜀ = 9 , Jₐ₆ = 4 )
976
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