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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5:18 minutes

Problem 58a

Textbook Question

The mass spectrum for a compound with molecular weight of 102 is shown below. Its IR spectrum has a broad, strong absorption at 3600 cm^–1 and a medium absorption at 1360 cm^–1.
a. Identify the compound.
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Verified step by step guidance

Step 1: Analyze the molecular weight of the compound, which is given as 102. This indicates the molecular ion peak (M+) in the mass spectrum should be at m/z = 102.

Step 2: Examine the IR spectrum data. The broad, strong absorption at 3600 cm⁻¹ suggests the presence of an -OH group, characteristic of alcohols. The medium absorption at 1360 cm⁻¹ indicates possible C-H bending vibrations, often associated with methyl groups.

Step 3: Look at the mass spectrum provided. The molecular ion peak (M+) at m/z = 102 confirms the molecular weight. Fragmentation patterns, such as peaks at m/z = 45 and m/z = 70, suggest possible loss of functional groups or fragments like CH3 or CH2OH.

Step 4: Combine the IR and mass spectrum data. The presence of an -OH group (from IR) and fragmentation patterns (from mass spectrum) suggest the compound is likely an alcohol. The molecular formula could be C4H10O, which matches the molecular weight of 102.

Step 5: Based on the data, the compound is likely butanol (C4H10O), as it fits the molecular weight, IR absorption characteristics, and fragmentation patterns observed in the mass spectrum.

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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 provides information about the molecular weight of a compound and its structural features. In the context of the question, the mass spectrum indicates a molecular ion peak corresponding to the molecular weight of 102, which helps in identifying the compound.

Infrared (IR) Spectroscopy

Infrared spectroscopy is a technique that measures the absorption of infrared light by a compound, providing information about its functional groups. The broad absorption at 3600 cm–1 suggests the presence of an -OH group, while the medium absorption at 1360 cm–1 may indicate a C-H bending vibration, which is common in alkanes or aromatic compounds.

Functional Group Identification

Identifying functional groups is crucial in organic chemistry as they determine the chemical reactivity and properties of compounds. The combination of mass spectrometry and IR spectroscopy data allows for the deduction of possible structures for the compound with a molecular weight of 102, guiding the identification process.

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Identify the peaks in the mass spectrum of octan-4-one that correspond to (a) α-cleavage.

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

(b)

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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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The mass spectrum of tert-butylamine follows shows an intense base peak at m/z 58, and very little else. Use a diagram to show the cleavage that accounts for the base peak. Suggest why no molecular ion is visible in this spectrum.

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Using curved arrows, show the principal fragments you would expect to see in the mass spectrum of each of the following compounds:

Textbook Question

The following compounds undergo McLafferty rearrangement in the mass spectrometer. Predict the masses of the resulting charged fragments.

(b) 3-methylhexan-2-one

Textbook Question

An acid-catalyzed reaction was carried out using methyl cellosolve (2-methoxyethanol) as the solvent. When the 2-methoxyethanol was redistilled, a higher-boiling fraction (bp 162°C) was also recovered. The mass spectrum of this fraction showed the molecular weight to be 134. The IR and NMR spectra are shown here. Determine the structure of this compound, and propose a mechanism for its formation.

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Textbook Question

The following spectra for A and B correspond to two structural isomers. The NMR singlet at δ1.16 in spectrum A disappears when the sample is shaken with D₂O. The singlet at δ0.6 ppm in the spectrum of B disappears on shaking with D₂O. Propose structures for these isomers, and show how your structures correspond to the spectra. Show what cleavage is responsible for the base peak at m/z 44 in the mass spectrum of A and the prominent peak at m/z 58 in the mass spectrum of B.

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The mass spectrum for a compound with molecular weight of 102 is shown below. Its IR spectrum has a broad, strong absorption at 3600 cm–1 and a medium absorption at 1360 cm–1.a. Identify the compound.<IMAGE>

Key Concepts

Mass Spectrometry

Infrared (IR) Spectroscopy

Functional Group Identification

Watch next

The mass spectrum for a compound with molecular weight of 102 is shown below. Its IR spectrum has a broad, strong absorption at 3600 cm^–1 and a medium absorption at 1360 cm^–1.
a. Identify the compound.
<IMAGE>