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 Complex Tree Diagrams

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

1H NMR:Spin-Splitting Complex Tree Diagrams

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7:29 minutes

Problem 12

Textbook Question

Draw a splitting tree, similar to Figures 13-32 and 13-33, for proton H^c in styrene. What is the chemical shift of proton H^c?

Verified step by step guidance

Identify the proton Hc in styrene. Styrene is an aromatic compound with a vinyl group attached to a benzene ring. Proton Hc is typically one of the protons in the vinyl group adjacent to the benzene ring.

Determine the coupling partners for proton Hc. In styrene, proton Hc will couple with the other protons in the vinyl group (Ha and Hb). Analyze the number of neighboring protons and their spin states to predict the splitting pattern.

Construct the splitting tree for proton Hc. Start with the initial peak for Hc, then split it based on the coupling with Ha (typically a doublet due to one neighboring proton). Next, split each peak of the doublet further due to coupling with Hb (another doublet, resulting in a doublet of doublets).

Estimate the chemical shift of proton Hc. The chemical shift depends on the electronic environment of Hc. Since Hc is part of the vinyl group adjacent to the benzene ring, it will experience deshielding due to the electron-withdrawing effect of the aromatic ring. This places its chemical shift in the range of approximately 5-6 ppm in a typical NMR spectrum.

Verify the splitting pattern and chemical shift using experimental data or reference spectra for styrene. Compare the predicted splitting tree and chemical shift with known values to ensure accuracy.

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Key Concepts

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

Chemical Shift

Chemical shift refers to the change in the resonant frequency of a nucleus in a magnetic field, influenced by the electronic environment surrounding it. In NMR spectroscopy, it is measured in parts per million (ppm) and provides insight into the molecular structure and the electronic effects of nearby atoms or groups. For protons, the chemical shift can indicate the presence of electronegative atoms or the degree of substitution in aromatic systems.

Splitting Patterns

Splitting patterns in NMR arise from the interaction of non-equivalent neighboring protons, which causes the resonance signals to split into multiple peaks. This phenomenon, known as spin-spin coupling, provides information about the number of adjacent protons and their arrangement. Understanding these patterns is crucial for interpreting the NMR spectrum and deducing the structure of the compound.

Aromatic Protons

Aromatic protons are those attached to carbon atoms in an aromatic ring, such as styrene. These protons typically exhibit unique chemical shifts due to the delocalized π-electrons in the aromatic system, which influence their electronic environment. The presence of substituents on the aromatic ring can further modify the chemical shifts and splitting patterns of these protons, making their analysis essential for structural determination.