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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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Multiple Choice

Pinacolone has a base peak in its mass spectrum at m/z 57. What is the structure corresponding to this mass?

The figure illustrates the structure of an ion. A 2-carbon alkane chain is depicted as a line structure using 1 line. C 2 carries a positive charge and is double bonded to O on the upper right.

The figure illustrates the structure of an ion. A 4-carbon alkane chain is depicted as a line structure using 3 zigzag lines. C 2 is single bonded to C H 3 below in the form of a line and carries a positive charge. C 3 is double bonded to O above.

The figure illustrates the structure of an ion. A 3-carbon alkane chain is depicted as a line structure using 2 zigzag lines. C 2 is single bonded to C H 3 above in the form of a line and carries a positive charge.

The figure illustrates the structure of a radical cation. A 4-carbon alkane chain is depicted as a line structure using 3 zigzag lines. C 2 is single bonded to C H 3 on the lower left and C H 3 on the lower right, each in the form of a line. C 3 is double bonded to O above. The entire structure is enclosed within square brackets with an unpaired electron and a superscript plus.

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Verified step by step guidance

Identify the molecular structure of pinacolone, which is a ketone with the formula (CH3)3C-C(=O)-CH3.

Understand that the base peak in a mass spectrum represents the most stable and abundant fragment ion.

Consider the fragmentation pattern of pinacolone. The loss of a methyl group (CH3) from the tert-butyl group ((CH3)3C-) is a common fragmentation pathway.

Calculate the mass of the resulting fragment ion after the loss of a methyl group. The tert-butyl cation ((CH3)2C+) is a stable carbocation with a mass of 57 amu.

Conclude that the structure corresponding to the m/z 57 peak is the tert-butyl cation, which is a common and stable fragment in the mass spectrum of pinacolone.