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

Carbon NMR

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

Carbon NMR

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Problem 46b

Textbook Question

How many signals would you expect in the ¹³C NMR spectrum of each molecule shown?
(b)

Verified step by step guidance

Identify the molecule in question. Understanding the structure is crucial for predicting the number of signals in the ¹³C NMR spectrum.

Recognize that each unique carbon environment in the molecule will produce a distinct signal in the ¹³C NMR spectrum. Carbons in identical environments will produce the same signal.

Examine the symmetry of the molecule. Symmetrical molecules often have fewer unique carbon environments because some carbons are equivalent due to symmetry.

Count the number of unique carbon environments. Look for differences in hybridization, connectivity, and the presence of functional groups that might affect the chemical environment of each carbon.

Consider any stereochemistry or conformational aspects that might influence the equivalence of carbon atoms. Sometimes, stereochemistry can lead to more unique environments than initially apparent.

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Key Concepts

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

Carbon-13 NMR Spectroscopy

Carbon-13 NMR spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic environment of carbon atoms. Each unique carbon environment in a molecule produces a distinct signal in the spectrum, allowing chemists to infer structural details based on the number and position of these signals.

Chemical Equivalence

Chemical equivalence refers to the condition where atoms or groups in a molecule are indistinguishable in terms of their chemical environment. In ¹³C NMR, chemically equivalent carbon atoms produce a single signal, as they experience the same magnetic field and have identical electronic surroundings, simplifying the spectrum analysis.

Symmetry in Molecules

Symmetry in molecules plays a crucial role in determining the number of NMR signals. Symmetrical molecules often have fewer unique carbon environments due to repeated structural units, leading to fewer signals. Recognizing symmetry helps predict the number of distinct signals in the ¹³C NMR spectrum, aiding in structural elucidation.

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