Textbook Question
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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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 43a
Mullins 1st EditionCh. 14 - Structural Identification I: Infrared Spectroscopy and Mass SpectrometryProblem 43aChapter 13, Problem 43a
Identify the peaks in the mass spectrum of octan-4-one that correspond to (a) α-cleavage.
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Verified step by step guidance1
Understand the concept of α-cleavage: In mass spectrometry, α-cleavage refers to the breaking of the bond adjacent to the carbonyl group in a ketone. This process generates a radical and a cation, which can be detected as peaks in the mass spectrum.
Identify the structure of octan-4-one: Octan-4-one is a ketone with an eight-carbon chain and a carbonyl group located at the fourth carbon. The molecular formula is C8H16O.
Determine the possible α-cleavage sites: For octan-4-one, α-cleavage can occur at the bonds adjacent to the carbonyl group, which are the C3-C4 and C4-C5 bonds.
Calculate the mass of the fragments: When α-cleavage occurs at the C3-C4 bond, the fragment containing the carbonyl group will be C4H8O. When cleavage occurs at the C4-C5 bond, the fragment will be C5H10O. Use the molecular weights of carbon (12), hydrogen (1), and oxygen (16) to calculate the mass of these fragments.
Identify the peaks in the mass spectrum: The mass spectrum will show peaks corresponding to the masses of the fragments generated by α-cleavage. Look for peaks at the calculated masses of C4H8O and C5H10O, which are the result of α-cleavage.
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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 generating a mass spectrum, which displays the masses of fragments. Understanding how to interpret these spectra is crucial for identifying molecular structures and fragmentation patterns.
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How to Read a Mass Spectrum
α-Cleavage
α-Cleavage is a common fragmentation process in mass spectrometry, particularly for carbonyl-containing compounds like ketones. It involves the breaking of the bond adjacent to the carbonyl group, resulting in the formation of a radical cation and a neutral fragment. This process helps identify specific structural features of the molecule.
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Fragmentation Patterns
Fragmentation patterns in mass spectrometry refer to the specific ways in which a molecule breaks apart into smaller ions. These patterns are influenced by the molecular structure and the stability of resulting fragments. Recognizing these patterns is essential for deducing the structure of the original molecule from its mass spectrum.
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Related Practice
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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Textbook Question
Assign the structure based on the mass spectrum and IR spectrum shown.
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