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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6:21 minutes

Problem 42(3)

Textbook Question

Describe the proton-coupled ¹³C NMR spectra for compound 3 in Problem 41, indicating the relative positions of the signals.
3.

Verified step by step guidance

Identify the structure of compound 3 from Problem 41. Analyze the molecular structure to determine the number of unique carbon environments. Each unique carbon environment corresponds to a distinct signal in the 13C NMR spectrum.

Determine the hybridization and bonding environment of each carbon atom in the molecule. For example, sp³ carbons (alkyl groups), sp² carbons (aromatic or alkene groups), and sp carbons (alkyne groups) will have different chemical shifts.

Consider the effects of proton coupling on the 13C NMR spectrum. In proton-coupled 13C NMR, each carbon signal is split into a multiplet based on the number of directly bonded hydrogens. Use the n+1 rule, where n is the number of hydrogens attached to the carbon, to predict the splitting pattern (e.g., singlet, doublet, triplet, etc.).

Analyze the relative positions of the signals in the spectrum. Electronegative groups, conjugation, or aromaticity can deshield carbons, causing downfield shifts (higher δ values). Conversely, alkyl groups or electron-donating groups can shield carbons, causing upfield shifts (lower δ values).

Summarize the expected 13C NMR spectrum by listing the approximate chemical shift ranges for each unique carbon, the splitting patterns due to proton coupling, and the relative intensities of the signals (if applicable).

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Key Concepts

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

Proton-Coupled 13C NMR Spectroscopy

Proton-coupled 13C NMR spectroscopy is a technique that provides information about the carbon environment in organic compounds by observing how carbon signals are influenced by nearby protons. In this method, the coupling between protons and carbon atoms leads to splitting patterns in the NMR signals, which can reveal the number of protons attached to each carbon and their spatial arrangement.

Chemical Shift

Chemical shift in NMR spectroscopy refers to the position of a signal in the spectrum, which is influenced by the electronic environment surrounding the nucleus. In 13C NMR, different functional groups and hybridization states of carbon atoms result in distinct chemical shifts, allowing chemists to deduce structural information about the compound being analyzed.

Signal Splitting Patterns

Signal splitting patterns in NMR arise from the interaction of nuclear spins, particularly between protons and carbons. The number of peaks in a signal corresponds to the number of equivalent protons on adjacent carbons, following the n+1 rule, where n is the number of neighboring protons. Understanding these patterns is crucial for interpreting the complexity of the NMR spectrum and deducing the molecular structure.

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Related Practice

Textbook Question

Answer the following questions for each compound:

a. How many signals are in its ¹³C NMR spectrum?

b. Which signal is at the lowest frequency?

9. CH₂=CHBr

Textbook Question

Answer the following questions for each compound:

a. How many signals are in its ¹³C NMR spectrum? b. Which signal is at the lowest frequency?

Textbook Question

Answer the following questions for each compound:

a. How many signals are in its ¹³C NMR spectrum?

b. Which signal is at the lowest frequency?

Textbook Question

Describe the proton-coupled ¹³C NMR spectra for compound 1 in Problem 41, indicating the relative positions of the signals.

1. CH₃CH₂CH₂Br

Textbook Question

Identify each compound below from its molecular formula and its ¹³C NMR spectrum.

a. C₁₁H₂₂O

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Textbook Question

Identify the compound with molecular formula C₇H₁₄O that gives the following proton-coupled ¹³C NMR spectrum:

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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.].

(a)

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)

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Describe the proton-coupled 13C NMR spectra for compound 3 in Problem 41, indicating the relative positions of the signals.3.

Key Concepts

Proton-Coupled 13C NMR Spectroscopy

Chemical Shift

Signal Splitting Patterns

Watch next

Describe the proton-coupled ¹³C NMR spectra for compound 3 in Problem 41, indicating the relative positions of the signals.
3.