Textbook Question
The mass spectra of 1-methoxybutane, 2-methoxybutane, and 2-methoxy-2-methylpropane are shown below. Match each compound with its spectrum.
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Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis 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
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Bruice 8th EditionCh. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis SpectroscopyProblem 14a
Bruice 8th EditionCh. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis SpectroscopyProblem 14aChapter 14, Problem 14a
Primary alcohols have a strong peak at m/z = 31.
a. What fragment is responsible for this peak?
Verified step by step guidance1
Identify the structure of a primary alcohol. A primary alcohol has the general formula R-CH2OH, where R is an alkyl group.
Understand the process of fragmentation in mass spectrometry. When a primary alcohol is ionized, it can break into smaller fragments, producing characteristic peaks in the mass spectrum.
Determine the fragment responsible for the peak at m/z = 31. The m/z value corresponds to the mass-to-charge ratio of the fragment. For m/z = 31, the fragment must have a molecular weight of 31 and a single positive charge.
Analyze the possible fragments of a primary alcohol. The hydroxymethyl group (CH2OH) is a common fragment in primary alcohols. Its molecular weight is calculated as follows: Carbon (12) + 2 Hydrogens (2 × 1) + Oxygen (16) = 31.
Conclude that the fragment responsible for the peak at m/z = 31 is the hydroxymethyl cation (CH2OH⁺), which forms when the primary alcohol undergoes fragmentation during ionization.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mass Spectrometry
Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio of ions. It helps in identifying the composition of a sample by generating a mass spectrum, which displays the different ions produced during ionization. Understanding mass spectrometry is crucial for interpreting the peaks in the spectrum, such as the one at m/z = 31 for primary alcohols.
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Fragmentation Patterns
Fragmentation patterns refer to the specific ways in which molecules break apart during mass spectrometry. Different functional groups and molecular structures lead to characteristic fragments. For primary alcohols, the peak at m/z = 31 typically corresponds to the loss of a hydroxyl group (–OH) and a hydrogen atom, resulting in the formation of a fragment ion that can be identified in the mass spectrum.
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Primary Alcohol Structure
Primary alcohols are organic compounds where the hydroxyl group (–OH) is attached to a carbon atom that is only connected to one other carbon atom. This structural characteristic influences their reactivity and fragmentation behavior in mass spectrometry. Recognizing the structure of primary alcohols is essential for understanding the origin of specific mass spectral peaks, including the one at m/z = 31.
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Related Practice
Textbook Question
Can a high-resolution mass spectrometer distinguish between them?
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Textbook Question
Predict the relative intensities of the molecular ion peak, the M+2 peak, and the M+4 peak for a compound that contains two bromine atoms.
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Textbook Question
Using curved arrows, show the principal fragments you would expect to see in the mass spectrum of each of the following compounds:
b.
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Textbook Question
Using curved arrows, show the principal fragments you would expect to see in the mass spectrum of each of the following compounds:
c.
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Textbook Question
Using curved arrows, show the principal fragments you would expect to see in the mass spectrum of each of the following compounds:
d.
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