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

NMR Practice

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

NMR Practice

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2:30 minutes

Problem 20

Textbook Question

Explain how the following compounds, each with the same molecular formula, could be distinguished by their ¹H NMR spectra.

Verified step by step guidance

Identify the molecular formula of the compounds and determine the degree of unsaturation (double bonds, rings, or triple bonds) to understand the structural possibilities.

Analyze the functional groups and structural features of each compound. Consider how these features influence the chemical environment of the hydrogen atoms (protons).

Predict the number of unique proton environments in each compound. This corresponds to the number of distinct signals in the 1H NMR spectrum.

Determine the chemical shift range for each type of proton based on its environment (e.g., alkyl, aromatic, aldehyde, etc.). Use the shielding and deshielding effects caused by electronegative atoms, π-systems, or other groups to estimate the approximate chemical shifts.

Consider the splitting patterns (multiplicity) of each signal, which arise from spin-spin coupling with neighboring protons. Use the n+1 rule (where n is the number of equivalent neighboring protons) to predict the splitting for each signal in the 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 exploits the magnetic properties of certain nuclei, primarily hydrogen-1 (1H), to provide information about the number and environment of hydrogen atoms in a molecule. The resulting spectrum displays peaks that correspond to different hydrogen environments, allowing chemists to infer structural details.

Chemical Shifts

Chemical shifts in an NMR spectrum indicate the resonance frequency of a nucleus relative to a standard reference. They are influenced by the electronic environment surrounding the hydrogen atoms, which can vary based on factors like electronegativity of nearby atoms and hybridization. Different compounds with the same molecular formula can exhibit distinct chemical shifts due to variations in their structural arrangements, leading to unique spectral patterns.

Integration and Multiplicity

Integration in NMR refers to the area under the peaks, which correlates to the number of hydrogen atoms contributing to that signal. Multiplicity describes the splitting of NMR signals into multiple peaks, which occurs due to spin-spin coupling between neighboring hydrogen atoms. Analyzing both integration and multiplicity helps distinguish between isomers with the same molecular formula, as they will show different patterns in their NMR spectra.

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06:46

1H NMR Integration

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Related Practice

Textbook Question

Draw the NMR spectra you expect for the following compounds.

(a)

Textbook Question

Identify each of the following compounds from its molecular formula and its ¹H NMR spectrum:

b. C₆H₁₂O

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Textbook Question

Identify each of the following compounds from the ¹H NMR data and molecular formula:

c. C₅H₁₀O₂: a 3H triplet at 1.15 ppm

a 3H triplet at 1.25 ppm

a 2H quartet at 2.33 ppm

a 2H quartet at 4.13 ppm

Textbook Question

Describe the ¹H NMR spectrum you would expect for each of the following compounds, indicating the relative positions of the signals:

Textbook Question

Describe the ¹H NMR spectrum you would expect for each of the following compounds, indicating the relative positions of the signals:

Textbook Question

Describe the ¹H NMR spectrum you would expect for each of the following compounds, indicating the relative positions of the signals:

g. CH₃CH₂OCH₂CH₃

Textbook Question

The following ¹H NMR spectra are for four compounds, each with molecular formula of C₆H₁₂O₂. Identify the compounds.

c. <IMAGE>

Textbook Question

Sketch the following spectra that would be obtained for 2-chloroethanol:

b. The ¹H NMR spectrum for a sample of the alcohol that contains a trace amount of acid.

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Explain how the following compounds, each with the same molecular formula, could be distinguished by their 1H NMR spectra.

Key Concepts

Nuclear Magnetic Resonance (NMR) Spectroscopy

Chemical Shifts

Integration and Multiplicity

Explain how the following compounds, each with the same molecular formula, could be distinguished by their ¹H NMR spectra.