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

Previous problemNext problem

Problem 66c

Textbook Question

For the molecules in Assessment 15.58, give an approximate chemical shift for each indicated carbon. [The range of correct answers is large here.].
(c)

Verified step by step guidance

Identify the type of carbon atom in the molecule. Determine if it is a primary, secondary, tertiary, or quaternary carbon, as this will influence the chemical shift.

Consider the electronic environment around the carbon atom. Check for any electronegative atoms or groups (like oxygen, nitrogen, or halogens) attached to or near the carbon, as they can deshield the carbon and increase the chemical shift.

Evaluate the hybridization of the carbon atom. For example, sp3 hybridized carbons typically have lower chemical shifts compared to sp2 or sp hybridized carbons.

Take into account any resonance effects. If the carbon is part of a conjugated system or an aromatic ring, this can also affect the chemical shift.

Estimate the chemical shift range based on the above factors. For example, sp3 carbons typically range from 0-50 ppm, sp2 carbons from 100-150 ppm, and sp carbons from 50-100 ppm in a 13C NMR spectrum.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Play a video:

Was this helpful?

Key Concepts

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

Chemical Shift in NMR Spectroscopy

Chemical shift is a key concept in NMR spectroscopy that refers to the resonant frequency of a nucleus relative to a standard in a magnetic field. It provides information about the electronic environment surrounding a nucleus, typically measured in parts per million (ppm). Factors such as electronegativity of nearby atoms and hybridization state can influence the chemical shift, making it a useful tool for structural analysis.

Factors Affecting Carbon Chemical Shifts

The chemical shift of carbon atoms in NMR is influenced by several factors, including the electronegativity of adjacent atoms, the hybridization of the carbon atom, and the presence of electron-withdrawing or electron-donating groups. For example, carbons bonded to electronegative atoms like oxygen or nitrogen typically show downfield shifts, while those in aliphatic chains are usually upfield.

Interpreting NMR Spectra

Interpreting NMR spectra involves analyzing the chemical shifts, signal splitting, and integration to deduce the structure of a molecule. Each carbon atom in a molecule can give rise to a distinct signal, and by comparing these shifts to known reference values, one can infer the type of carbon environment present. This process is crucial for identifying functional groups and understanding molecular architecture.