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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6:11 minutes

Problem 57a

Textbook Question

How many distinct signals would you expect to see in the ¹H NMR spectrum of the following molecules? [Ignore diastereotopic hydrogens for the sake of this assessment.]
(a)

Verified step by step guidance

Identify the unique hydrogen environments in the molecule. Each unique environment will correspond to a distinct signal in the ¹H NMR spectrum.

Consider the symmetry of the molecule. Symmetrical molecules often have fewer unique hydrogen environments because equivalent hydrogens will produce the same signal.

Look for different types of hydrogens such as those attached to sp3 hybridized carbons, sp2 hybridized carbons, and any hydrogens involved in functional groups like alcohols or amines.

Count the number of unique hydrogen environments. This will give you the number of distinct signals expected in the ¹H NMR spectrum.

Remember to ignore diastereotopic hydrogens as per the problem's instructions, focusing only on the unique environments that are not diastereotopic.

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Key Concepts

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

¹H NMR Spectroscopy

¹H NMR spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic environment of hydrogen atoms. Each distinct hydrogen environment in a molecule produces a separate signal in the NMR spectrum, allowing chemists to infer the number and type of hydrogen atoms present.

Chemical Equivalence

Chemical equivalence refers to hydrogen atoms in a molecule that are in identical environments and thus produce the same NMR signal. Identifying chemically equivalent hydrogens is crucial for predicting the number of distinct signals in an NMR spectrum, as equivalent hydrogens contribute to a single peak.

Symmetry in Molecules

Symmetry in molecules can lead to chemical equivalence among hydrogen atoms, reducing the number of distinct NMR signals. Recognizing symmetry elements, such as mirror planes or rotational axes, helps determine which hydrogens are equivalent and simplifies the analysis of the NMR spectrum.

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Related Practice

Textbook Question

How many unique ¹H NMR signals would you expect in an NMR spectrum for the following molecules?

(c)

Textbook Question

How many sets of equivalent hydrogens are present in the molecule that resulted in this NMR spectrum? [Recall that some signals can be split into multiple peaks—they are still just one signal.]

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Textbook Question

Without worrying about the relative location of the signals (i.e., the chemical shift) or the splitting patterns, draw a spectrum of the following molecule. Be sure to label each signal based on the set of equivalent hydrogens to which it corresponds.

Textbook Question

Replace Hₐ and H₆ in hexane with a deuterium. What is the relationship between the two products you obtain? Based on this, would you expect the two hydrogens to give one or two signals in the ¹H NMR spectrum?

Textbook Question

How many distinct signals would you expect to see in the ¹H NMR spectrum of the following molecules? [Ignore diastereotopic hydrogens for the sake of this assessment.]

(b)

Textbook Question

How many distinct signals would you expect to see in the ¹H NMR spectrum of the following molecules? [Ignore diastereotopic hydrogens for the sake of this assessment.]

(c)

Textbook Question

How many distinct signals would you expect to see in the ¹H NMR spectrum of the following molecules? [Ignore diastereotopic hydrogens for the sake of this assessment.]

(f)

Textbook Question

Radical chlorination, a reaction studied in Chapters 5 and 11, replaces a hydrogen with a chlorine. Assuming there is no regioselectivity (all hydrogens can react equally), how many different chloroalkanes are possible upon reaction of each alkane with one equivalent of Cl₂

(a)

(b)

(c)

(d)

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