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:Number of Signals

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

1H NMR:Number of Signals

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3:40 minutes

Problem 4m,n,o

Textbook Question

How many signals would you expect to see in the 1H NMR spectrum of each of the following compounds?
m.
n.
o.

Verified step by step guidance

Step 1: Analyze the structure of the compound. The compound consists of a benzene ring and a carbon atom attached to three nitro groups (-NO2). The benzene ring is symmetric, and the substituent (C(NO2)3) is attached to one of its carbons.

Step 2: Determine the symmetry of the molecule. The benzene ring is symmetric, and the substituent does not disrupt this symmetry. This means that equivalent hydrogens on the benzene ring will give the same signal in the 1H NMR spectrum.

Step 3: Identify the unique hydrogen environments. In the benzene ring, there are two sets of equivalent hydrogens due to the symmetry: (a) two hydrogens ortho to the substituent, and (b) two hydrogens meta to the substituent. The para hydrogen is unique and forms a third environment.

Step 4: Count the number of signals. Since there are three unique hydrogen environments in the benzene ring, the 1H NMR spectrum will show three distinct signals.

Step 5: Consider splitting patterns and chemical shifts. The splitting patterns will depend on the coupling between hydrogens in adjacent environments, and the chemical shifts will be influenced by the electron-withdrawing effect of the nitro groups. However, the number of signals remains three.

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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, primarily hydrogen (1H), to provide information about the number of distinct hydrogen environments in a molecule. Each unique hydrogen environment produces a separate signal in the NMR spectrum, allowing chemists to infer structural details.

Chemical Shifts

Chemical shifts in NMR spectroscopy refer to the variation in resonance frequency of nuclei due to their electronic environment. Different functional groups and molecular structures influence the electron density around hydrogen atoms, leading to shifts in their resonance signals. Understanding chemical shifts helps in predicting the number of signals and their positions in the spectrum, which is crucial for interpreting NMR data.

Symmetry and Equivalent Protons

In organic molecules, symmetry can lead to equivalent protons, which are protons that experience the same electronic environment and thus produce a single NMR signal. Analyzing the symmetry of a compound helps in determining how many unique signals will appear in the NMR spectrum. For the nitro-substituted benzene compound shown, recognizing the symmetry and the effects of substituents is essential for predicting the number of signals.

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