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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6:45 minutes

Problem 65

Textbook Question

The ¹H NMR spectrum of 2-propen-1-ol is shown here. Indicate the protons in the molecule that are responsible for each of the signals in the spectrum.
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Verified step by step guidance

Step 1: Analyze the molecular structure of 2-propen-1-ol (CH2=CH-CH2OH). It contains three types of protons: the vinyl protons (CH2=CH), the methylene protons (CH2OH), and the hydroxyl proton (-OH).

Step 2: Examine the 1H NMR spectrum. The chemical shift values (in ppm) and splitting patterns provide clues about the environment of each proton type. For example, vinyl protons typically appear downfield (higher ppm), while methylene and hydroxyl protons appear upfield (lower ppm).

Step 3: Assign the signal at approximately 4 ppm to the hydroxyl proton (-OH). This proton is deshielded due to its attachment to the electronegative oxygen atom.

Step 4: Assign the signal at approximately 3 ppm to the methylene protons (CH2OH). These protons are slightly deshielded due to their proximity to the hydroxyl group.

Step 5: Assign the signal at approximately 2 ppm to the vinyl protons (CH2=CH). These protons are deshielded due to the electron-withdrawing effect of the double bond.

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Key Concepts

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

Proton NMR Spectroscopy

Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic environment of hydrogen atoms in a molecule. Each unique hydrogen environment produces a signal at a specific chemical shift (measured in ppm), allowing chemists to infer the number and type of protons present.

Chemical Shift

Chemical shift refers to the position of a signal in the NMR spectrum, which indicates the electronic environment surrounding the hydrogen atoms. Protons in different environments (e.g., near electronegative atoms or in aliphatic vs. aromatic regions) resonate at different frequencies, leading to distinct peaks in the spectrum that can be used to identify functional groups and molecular structure.

Integration and Multiplicity

Integration in NMR refers to the area under a peak, which correlates to the number of protons contributing to that signal. Multiplicity indicates the splitting pattern of the peaks, which arises from neighboring protons (n+1 rule). Understanding these concepts helps in determining how many protons are in each environment and their connectivity within the molecule.

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Guided course

06:46

1H NMR Integration

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Related Practice

Textbook Question

Given the ¹H NMR spectrum and the molecular formula, suggest a structure for each molecule. [The IR spectrum suggests the presence of two C=O bonds.]

(a) Important IR bands (cm ⁻ ¹) : 1728, 1708 [Note: The pKₐ of this molecule is around 10.]

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Textbook Question

A small pilot plant was adding bromine across the double bond of but-2-ene to make 2,3-dibromobutane. A controller malfunction allowed the reaction temperature to rise beyond safe limits. A careful distillation of the product showed that several impurities had formed, including the one having the NMR spectra that appear below. Determine its structure, and assign the peaks to the protons in your structure.

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Textbook Question

Identify pairs of coupled protons in the compound whose COSY spectrum is shown below.

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Textbook Question

What does cross peak X in Figure 14.34 tell you?

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Open Question

Draw the approximate positions that the following compound might show in its 1H NMR absorptions?

Open Question

Draw the approximate positions that the following compound might show in its 1H NMR absorptions?

Multiple Choice

A ¹H NMR spectrum has a singlet at 4.1 ppm with an integration of 2H. How many hydrogen atoms are on the neighboring carbon atom?

Multiple Choice

A ¹H NMR spectrum contains a quartet at 4.1 ppm integrating to 2H and triplet at 0.9 ppm integrating to 3H, among other signals. What fragment is likely part of this molecule?

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The 1H NMR spectrum of 2-propen-1-ol is shown here. Indicate the protons in the molecule that are responsible for each of the signals in the spectrum.<IMAGE>

Key Concepts

Proton NMR Spectroscopy

Chemical Shift

Integration and Multiplicity

The ¹H NMR spectrum of 2-propen-1-ol is shown here. Indicate the protons in the molecule that are responsible for each of the signals in the spectrum.
<IMAGE>