Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

15. Analytical Techniques:IR, NMR, Mass Spect

Mass Spect:Fragmentation

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

Mass Spect:Fragmentation

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Problem 37

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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Verified step by step guidance

Identify the structure of hexan-3-ol: It is a six-carbon chain alcohol with the hydroxyl group (-OH) on the third carbon. The molecular formula is C6H14O.

Understand α-cleavage: In mass spectrometry, α-cleavage involves breaking the bond adjacent to the carbon bearing the functional group. For hexan-3-ol, this means breaking the C-C bonds adjacent to the carbon with the -OH group.

Perform the first α-cleavage: Break the bond between the second and third carbon atoms. This results in a fragment with a positive charge on the second carbon, forming a C2H5+ ion and a neutral fragment.

Perform the second α-cleavage: Break the bond between the third and fourth carbon atoms. This results in a fragment with a positive charge on the third carbon, forming a C3H7+ ion and a neutral fragment.

Consider dehydration fragmentation: Dehydration involves the loss of a water molecule (H2O) from the alcohol. In hexan-3-ol, this typically occurs by removing the hydroxyl group and a hydrogen from an adjacent carbon, resulting in the formation of an alkene fragment with a double bond.

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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 molecules break apart in a mass spectrometer is crucial for interpreting the spectrum and identifying molecular fragments.

α-Cleavage

α-Cleavage in mass spectrometry involves the breaking of a bond adjacent to a functional group, such as an alcohol group in hexan-3-ol. This process results in the formation of a radical and a cation. Identifying the specific bonds that undergo α-cleavage helps determine the resulting fragments in the mass spectrum.

Dehydration Fragmentation

Dehydration fragmentation is a common reaction in mass spectrometry for alcohols, where a water molecule (H2O) is eliminated. This process typically results in the formation of an alkene. Recognizing dehydration is essential for identifying the characteristic mass loss of 18 amu, corresponding to the removal of water, in the mass spectrum.

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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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For each of the molecules shown, predict the structure of at least one major fragment in the mass spectrum.

(d)

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For each of the molecules shown, predict the structure of at least one major fragment in the mass spectrum.

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In the mass spectrum of hexan-3-ol, identify the fragments arising from two α-cleavage fragmentations and one dehydration fragmentation.<IMAGE>

Key Concepts

Mass Spectrometry

α-Cleavage

Dehydration Fragmentation

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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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