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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3:12 minutes

Problem 78b(5)

Textbook Question

How many signals are produced by each of the following compounds in its
b. ¹³C NMR spectrum?
5.

Verified step by step guidance

Analyze the structure of the compound: The given compound is bromocyclopropane with two methyl groups attached to the cyclopropane ring. The bromine atom is bonded to one of the carbons in the cyclopropane ring.

Determine the symmetry of the molecule: The molecule has a plane of symmetry passing through the bromine atom and the cyclopropane ring. This symmetry will help identify equivalent carbons.

Identify the unique carbon environments: In 13C NMR, each unique carbon environment produces a distinct signal. The cyclopropane ring has three carbons, but due to symmetry, two of them are equivalent. The methyl groups are also equivalent to each other.

Count the number of unique carbon environments: There are three unique carbon environments in this molecule: (1) the carbon bonded to bromine, (2) the two equivalent carbons in the cyclopropane ring, and (3) the two equivalent methyl carbons.

Conclude the number of signals: Based on the analysis, the compound will produce three distinct signals in its 13C NMR spectrum.

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Key Concepts

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

Nuclear Magnetic Resonance (NMR) Spectroscopy

NMR spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It relies on the magnetic properties of certain nuclei, such as carbon-13 (13C), to provide information about the environment surrounding these nuclei. In 13C NMR, each unique carbon environment in a molecule produces a distinct signal, allowing chemists to infer structural details.

Chemical Shifts

Chemical shifts in NMR spectroscopy refer to the variation in resonance frequency of a nucleus due to its electronic environment. In 13C NMR, the chemical shift is influenced by factors such as electronegativity of nearby atoms and hybridization of the carbon atom. Understanding chemical shifts helps in identifying the types of carbon environments present in a compound, which is crucial for interpreting the NMR spectrum.

Signal Counting in NMR

The number of signals observed in an NMR spectrum corresponds to the number of distinct carbon environments in a molecule. Equivalent carbons, which are in the same electronic environment, will produce a single signal, while non-equivalent carbons will produce separate signals. Analyzing the structure of the compound allows chemists to predict how many unique signals will appear in the 13C NMR spectrum.

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Related Practice

Textbook Question

A laboratory student was converting cyclohexanol to cyclohexyl bromide by using one equivalent of sodium bromide in a large excess of concentrated sulfuric acid. The major product she recovered was not cyclohexyl bromide, but a compound of formula C₆H₁₀ that gave the following ¹³C NMR spectrum:

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(a) Propose a structure for this product.

(b) Assign the peaks in the ¹³C NMR spectrum to the carbon atoms in the structure.

Textbook Question

An inexperienced graduate student was making some 4-hydroxybutanoic acid. He obtained an excellent yield of a different compound, whose ¹³C NMR spectrum is shown here.

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(a) Propose a structure for this product.

(b) Assign the peaks in the ¹³C NMR spectrum to the carbon atoms in the structure.

Textbook Question

A bottle of allyl bromide was found to contain a large amount of an impurity. A careful distillation separated the impurity, which has the molecular formula C₃H₆O. The following ¹³C NMR spectrum of the impurity was obtained:

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(a) Propose a structure for this impurity.

(b) Assign the peaks in the ¹³C NMR spectrum to the carbon atoms in the structure.

Textbook Question

How many signals are produced by each of the following compounds in its

b. ¹³C NMR spectrum?

Textbook Question

How many signals are produced by each of the following compounds in its

b. ¹³C NMR spectrum?

Textbook Question

Would it be better to use ¹H NMR or ¹³C NMR spectroscopy to distinguish 1-butene, cis-2-butene, and 2-methylpropene? Explain your answer.

Textbook Question