Textbook Question
Sketch the following spectra that would be obtained for 2-chloroethanol:
d. The proton-coupled 13C NMR spectrum.
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Ch. 14 - NMR Spectroscopy
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 15, Problem 69b
Sketch the following spectra that would be obtained for 2-chloroethanol:
b. The 1H NMR spectrum for a sample of the alcohol that contains a trace amount of acid.
Verified step by step guidance1
Identify the structure of 2-chloroethanol (ClCH2CH2OH) and determine the types of protons present. There are three distinct types of protons: (1) the protons on the CH2 group attached to the chlorine atom, (2) the protons on the CH2 group attached to the hydroxyl group, and (3) the hydroxyl proton (OH).
Consider the effect of a trace amount of acid in the sample. The acid can cause rapid exchange of the hydroxyl proton (OH) with other protons in the solution, leading to broadening or disappearance of the OH signal in the 1H NMR spectrum.
Analyze the chemical shifts for the remaining protons: (1) The CH2 group attached to the electronegative chlorine atom will appear downfield (higher ppm) due to deshielding. (2) The CH2 group attached to the hydroxyl group will also be deshielded but to a lesser extent than the CH2 group attached to chlorine.
Determine the splitting patterns for each type of proton: (1) The CH2 group attached to chlorine will be split into a triplet due to coupling with the adjacent CH2 group (n+1 rule, where n = 2). (2) The CH2 group attached to the hydroxyl group will also be split into a triplet due to coupling with the adjacent CH2 group. The OH proton typically does not show splitting due to rapid exchange in the presence of acid.
Sketch the spectrum: (1) A triplet for the CH2 group attached to chlorine at a downfield position (higher ppm). (2) A triplet for the CH2 group attached to the hydroxyl group at a slightly upfield position (lower ppm compared to the first triplet). (3) The OH signal may be absent or appear as a broad peak depending on the exchange rate with the acid.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nuclear Magnetic Resonance (NMR) Spectroscopy
NMR spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It relies on the magnetic properties of certain nuclei, such as hydrogen-1 (1H), to provide information about the environment of atoms within a molecule. In 1H NMR, the chemical shifts, splitting patterns, and integration of peaks reveal details about the number of hydrogen atoms and their connectivity.
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General NMR Features
Chemical Shifts
Chemical shifts in NMR spectroscopy refer to the resonance frequency of a nucleus relative to a standard reference, typically tetramethylsilane (TMS). They are measured in parts per million (ppm) and provide insight into the electronic environment surrounding the hydrogen atoms. For 2-chloroethanol, the presence of electronegative atoms like chlorine and oxygen will influence the chemical shifts, causing them to appear downfield (at higher ppm values).
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Spin-Spin Coupling
Spin-spin coupling, or J-coupling, occurs when non-equivalent hydrogen atoms influence each other's magnetic environments, leading to splitting of NMR signals. This results in multiplet patterns that provide information about the number of neighboring hydrogen atoms. In the case of 2-chloroethanol, the splitting pattern will help identify the connectivity of the hydrogen atoms on the carbon chain, revealing the presence of adjacent protons.
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Related Practice
Textbook Question
Sketch the following spectra that would be obtained for 2-chloroethanol:
a. The 1H NMR spectrum for an anhydrous sample of the alcohol.
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Textbook Question
Sketch the following spectra that would be obtained for 2-chloroethanol:
c. The 13C NMR spectrum.
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Textbook Question
The 1H NMR spectrum of 2-propen-1-ol is shown here. Indicate the protons in the molecule that are responsible for each of the signals in the spectrum.
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Textbook Question
Draw a splitting diagram for the Hb proton if Jbc = 10 and Jba = 5.
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Textbook Question
Sketch the following spectra that would be obtained for 2-chloroethanol:
e. The four parts of a DEPT 13C NMR spectrum.
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