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 45a

Textbook Question

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

Verified step by step guidance

Identify the hydrogen atom labeled as Hₐ in the molecular structure. This is the hydrogen for which we need to predict the NMR signals.

Determine the number of neighboring hydrogen atoms (n) that are coupled to Hₐ. This will help in predicting the splitting pattern of the signal.

Use the n+1 rule to predict the splitting pattern of the signal for Hₐ. The n+1 rule states that a hydrogen atom with n neighboring hydrogens will split into n+1 peaks.

Consider the given coupling constants (J values) to determine the spacing between the peaks in the splitting pattern. The coupling constant is the distance between the peaks in Hz.

Sketch the expected NMR signal for Hₐ, showing the correct number of peaks and the spacing between them based on the coupling constants provided.

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Key Concepts

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

NMR Spectroscopy

Nuclear Magnetic Resonance (NMR) spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic properties of atomic nuclei. In NMR, hydrogen atoms (protons) in a molecule produce signals that can be interpreted to reveal information about the chemical environment and connectivity of the atoms.

Chemical Shift

Chemical shift refers to the position of an NMR signal on the spectrum, measured in parts per million (ppm). It indicates the electronic environment surrounding a nucleus, with shifts affected by factors such as electronegativity and hybridization of nearby atoms. Understanding chemical shifts helps predict where a proton signal will appear in the NMR spectrum.

Spin-Spin Coupling

Spin-spin coupling, or J-coupling, occurs when magnetic interactions between neighboring nuclei cause splitting of NMR signals into multiple peaks. The coupling constant (J) quantifies the degree of splitting and is measured in Hertz (Hz). Recognizing coupling patterns is essential for interpreting complex NMR spectra and determining molecular structure.

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Related Practice

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

Draw the expected signal for a hydrogen with the following coupling constants.

(b) Hₐ : δ 3.34 (Jₐ꜀ = 9 , Jₐ₆ = 4 )

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 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.

Textbook Question

Draw a diagram like the one shown in Figure 14.12 to predict

a. the relative intensities of the peaks in a triplet.

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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)