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

1H NMR:Spin-Splitting Simple Tree Diagrams

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

1H NMR:Spin-Splitting Simple Tree Diagrams

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Problem 40b

Textbook Question

Draw the expected signal for a hydrogen with the following coupling constants.
(b) Hₐ : δ 3.34 (Jₐ꜀ = 9 , Jₐ₆ = 4 )

Verified step by step guidance

Identify the hydrogen atom in question, Hₐ, and note its chemical shift, δ 3.34, which indicates where the signal will appear on the NMR spectrum.

Understand the coupling constants provided: Jₐ꜀ = 9 Hz and Jₐ₆ = 4 Hz. These values indicate the splitting pattern of the signal due to neighboring hydrogens.

Determine the number of neighboring hydrogens that cause the splitting. The coupling constant Jₐ꜀ = 9 Hz suggests a strong coupling with one set of hydrogens, while Jₐ₆ = 4 Hz suggests a weaker coupling with another set.

Predict the splitting pattern based on the coupling constants. A larger coupling constant typically indicates a doublet, while a smaller one might suggest further splitting. Consider the possibility of a doublet of doublets.

Draw the expected NMR signal for Hₐ, showing the splitting pattern as a doublet of doublets, with the larger coupling constant (9 Hz) causing the initial split and the smaller constant (4 Hz) causing further splitting of each peak.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chemical Shift (δ)

Chemical shift (δ) is a measure of the resonance frequency of a nucleus relative to a standard in a magnetic field. It is expressed in parts per million (ppm) and provides information about the electronic environment surrounding the nucleus. In this question, δ 3.34 indicates the position of the hydrogen signal on the NMR spectrum, suggesting the hydrogen is in a relatively deshielded environment.

Coupling Constants (J)

Coupling constants (J) are a measure of the interaction between nuclear spins and are expressed in hertz (Hz). They provide information about the number of neighboring hydrogens and their spatial relationship. In this question, Jₐ꜀ = 9 Hz and Jₐ₆ = 4 Hz indicate the hydrogen is coupled to two different sets of neighboring hydrogens, leading to a splitting pattern in the NMR signal.

NMR Splitting Patterns

NMR splitting patterns arise from spin-spin coupling between non-equivalent hydrogens. The number of peaks in a splitting pattern is determined by the n+1 rule, where n is the number of neighboring hydrogens. In this case, the hydrogen with coupling constants Jₐ꜀ = 9 Hz and Jₐ₆ = 4 Hz will exhibit a complex splitting pattern, reflecting its interactions with two different sets of neighboring hydrogens.

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Related Practice

Textbook Question

For the hydrogen(s) screened in blue, draw the signal you would expect to see in a ¹H NMR spectrum. At which chemical shift would the signal appear?

(c)

Textbook Question

For the hydrogen(s) screened in blue, draw the signal you would expect to see in a ¹H NMR spectrum. At which chemical shift would the signal appear?

(e)

Textbook Question

Predict the splitting pattern for each of the indicated hydrogens in Assessment 15.59.

(d)

Textbook Question

A chemist made what was thought to be compound A or B. How could coupling constants between H_a and H_b be used to distinguish between the two isomers? [Hint: Draw a chair conformation of each.]

Textbook Question

Though it wasn't discussed, what coupling constant would you expect for Hₐ and H꜀ in the spectrum of trans-but-2-enoic acid in Figure 15.50? Justify your answer.

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Textbook Question

Sketch the signals you would expect to see for Hₐ in the molecule shown. The important coupling constants are given.

Textbook Question

Sketch the signals you would expect to see for H_b in the molecule shown. The important coupling constants are given.

Textbook Question

Sketch the signals you would expect to see for H꜀ in the molecule shown. The important coupling constants are given.

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Draw the expected signal for a hydrogen with the following coupling constants. (b) Hₐ : δ 3.34 (Jₐ꜀ = 9 , Jₐ₆ = 4 )

Key Concepts

Chemical Shift (δ)

Coupling Constants (J)

NMR Splitting Patterns

Watch next

Draw the expected signal for a hydrogen with the following coupling constants.
(b) Hₐ : δ 3.34 (Jₐ꜀ = 9 , Jₐ₆ = 4 )