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 41
Mullins 1st EditionCh. 14 - Structural Identification I: Infrared Spectroscopy and Mass SpectrometryProblem 41Chapter 13, Problem 41
The base peak in Figure 14.51 has m/z 45. Suggest a molecular formula and a structure for this fragment.
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Understand that the base peak in a mass spectrum represents the most abundant ion, and its m/z value is crucial for deducing the structure of the fragment.
The m/z value of 45 suggests a fragment with a molecular weight of 45. Consider common organic fragments that could have this mass.
Calculate possible molecular formulas that sum to a molecular weight of 45. For example, consider C3H9N (molecular weight: 3*12 + 9*1 + 14 = 45) or C2H5O (molecular weight: 2*12 + 5*1 + 16 = 45).
Evaluate the chemical plausibility of each formula by considering typical fragmentation patterns in mass spectrometry. For instance, C2H5O could represent an ethoxy group, which is a common fragment.
Propose a structure for the fragment based on the plausible molecular formula. For example, if C2H5O is considered, the structure could be an ethoxy group (CH3CH2O).
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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 (m/z) of ions. It helps identify the composition of a sample by analyzing the mass of its fragments. The base peak represents the most abundant ion, providing clues about the structure of the molecule.
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How to Read a Mass Spectrum
Fragmentation Patterns
Fragmentation patterns in mass spectrometry refer to the way molecules break apart into smaller ions. Understanding these patterns is crucial for deducing the structure of the original molecule. The m/z value of a fragment can suggest possible molecular formulas and structural components.
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Molecular Formula Determination
Determining a molecular formula involves calculating the possible combinations of atoms that match the observed m/z value. This requires knowledge of atomic masses and common molecular fragments. For m/z 45, potential fragments could include C3H9N or C2H5O, guiding the identification of the structure.
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Related Practice
Textbook Question
Identify the peaks in the mass spectrum of octan-4-one that correspond to (a) α-cleavage.
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Textbook Question
Identify the peaks in the mass spectrum of octan-4-one that correspond to (b) the McLafferty rearrangement.
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Textbook Question
Suggest three ways that the following tertiary amine can fragment by α-cleavage. At which m/z would you expect to see peaks corresponding to these fragments?
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Textbook Question
In the mass spectrum of hexan-3-ol, identify the fragments arising from two α-cleavage fragmentations and one dehydration fragmentation.
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Textbook Question
2-Methylnonan-4-one can undergo two different McLafferty rearrangements. Draw the products of each of them.
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