Textbook Question
Besides the molecular mass, how do you know that the fragment that gives rise to the peak at m/z 111 in the mass spectrum for 1-bromo-4-chlorobenzene contains only chlorine?
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Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry
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. 14 - Structural Identification I: Infrared Spectroscopy and Mass SpectrometryProblem 29
Mullins 1st EditionCh. 14 - Structural Identification I: Infrared Spectroscopy and Mass SpectrometryProblem 29Chapter 13, Problem 29
The molecule that gave the mass spectrum shown here contains a halogen. Which halogen is present?
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Examine the mass spectrum for the presence of a molecular ion peak and its isotopic pattern. Halogens have characteristic isotopic patterns that can help identify them.
Identify the molecular ion peak (M) in the mass spectrum. This peak represents the molecular weight of the compound.
Look for additional peaks that are close in mass to the molecular ion peak. Halogens like chlorine and bromine have isotopes that create distinct patterns.
For chlorine, expect a pattern with two peaks: M and M+2, with a relative intensity ratio of approximately 3:1 due to the presence of 35Cl and 37Cl isotopes.
For bromine, expect a pattern with two peaks: M and M+2, with a relative intensity ratio of approximately 1:1 due to the presence of 79Br and 81Br isotopes.
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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 identify the composition of a sample by producing a mass spectrum, which displays the masses of the components. In organic chemistry, it is often used to determine the molecular weight and structure of compounds, including the presence of specific elements like halogens.
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Isotopic Patterns of Halogens
Halogens such as chlorine and bromine have characteristic isotopic patterns that are visible in mass spectra. Chlorine has two main isotopes, 35Cl and 37Cl, with a natural abundance ratio of about 3:1, while bromine has 79Br and 81Br with a 1:1 ratio. These patterns create distinct peaks in the mass spectrum, aiding in the identification of the specific halogen present.
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Fragmentation in Mass Spectrometry
Fragmentation is the process by which a molecule breaks into smaller pieces in a mass spectrometer. This occurs after ionization and can provide structural information about the molecule. The pattern of fragmentation, including the presence of specific fragment ions, can help identify functional groups and elements, such as halogens, within the molecule.
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Related Practice
Textbook Question
Match each of the four IR spectra to one of the given compounds. [One of the compounds does not match a spectrum.]
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Textbook Question
Match each of the four IR spectra to one of the given compounds. [One of the compounds does not match a spectrum.]
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Textbook Question
For each pair, choose the molecule that you expect to have the highest wavenumber for its C=O stretch.
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Textbook Question
The presence of what atom is indicated by the following mass spectrum?
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Textbook Question
The molecular ion (M) is significant in the mass spectrum of benzyl fluoride, but it is barely present in the mass spectrum of benzyl iodide. Why might this be the case?
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