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

NMR Practice

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

NMR Practice

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Multiple Choice

A ¹H NMR spectrum contains a quartet at 4.1 ppm integrating to 2H and triplet at 0.9 ppm integrating to 3H, among other signals. What fragment is likely part of this molecule?

An ethyl group

A methyl group

An isopropyl group.

A t-butyl group

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Verified step by step guidance

Identify the splitting pattern of the signals: A quartet indicates a CH2 group adjacent to a CH3 group, and a triplet indicates a CH3 group adjacent to a CH2 group.

Consider the integration values: The quartet integrates to 2H, suggesting it corresponds to a CH2 group, and the triplet integrates to 3H, suggesting it corresponds to a CH3 group.

Recognize the chemical shift values: The quartet at 4.1 ppm is downfield, indicating the CH2 group is likely near an electronegative atom or group, while the triplet at 0.9 ppm is upfield, typical for a CH3 group in an alkyl chain.

Combine the splitting pattern, integration, and chemical shift information: The combination of a CH2 group (quartet) and a CH3 group (triplet) with the given chemical shifts is characteristic of an ethyl group.

Conclude that the fragment is an ethyl group, as it matches the observed NMR data with a CH2-CH3 structure, where the CH2 is deshielded, causing the downfield shift.

Related Practice

Textbook Question

The ¹H NMR spectrum of 2-propen-1-ol is shown here. Indicate the protons in the molecule that are responsible for each of the signals in the spectrum.

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Open Question

Draw the approximate positions that the following compound might show in its 1H NMR absorptions?

Open Question

Draw the approximate positions that the following compound might show in its 1H NMR absorptions?

Multiple Choice

A ¹H NMR spectrum has a singlet at 4.1 ppm with an integration of 2H. How many hydrogen atoms are on the neighboring carbon atom?

Multiple Choice

Which of the following structures would give the following ¹H NMR spectrum?0.93 ppm (s, 9H), 2.13 ppm (d, 2H), 9.85 ppm (t, 1H)

Textbook Question

Draw the expected NMR spectrum of methyl propionate, and point out how it differs from the spectrum of ethyl acetate.

Textbook Question

Each of these four structures has molecular formula C₄H₈O₂. Match the structure with its characteristic proton NMR signals. (Not all of the signals are listed in each case.)

(a) sharp 1H singlet at δ8.0 and 2H triplet at δ4.0

(b) sharp 3H singlet at δ2.0 and 2H quartet at δ4.1

(d) broad 1H singlet at δ11.5 and 2H triplet at δ2.3

Textbook Question

Tell precisely how you would use the proton NMR spectra to distinguish between the following pairs of compounds.

(b)

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