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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3:51 minutes

Problem 15c

Textbook Question

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

Verified step by step guidance

Identify the molecule in question. Understanding the structure is crucial for predicting the number of unique ¹H NMR signals.

Examine the symmetry of the molecule. Symmetrical molecules often have fewer unique signals because equivalent hydrogens produce the same signal.

Determine the different types of hydrogen environments present in the molecule. Hydrogens in different chemical environments will produce distinct signals.

Consider the presence of chiral centers or stereochemistry, as these can affect the equivalence of hydrogen atoms and thus the number of signals.

Count the number of unique hydrogen environments. Each unique environment corresponds to a unique ¹H NMR signal.

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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 (Proton Nuclear Magnetic Resonance) spectroscopy is a technique used to determine the structure of organic compounds by analyzing the magnetic environment of hydrogen atoms. Each unique hydrogen environment in a molecule produces a distinct signal in the NMR spectrum, allowing chemists to deduce the number and types of hydrogen atoms present.

Chemical Equivalence

Chemical equivalence in NMR refers to hydrogen atoms that are in identical environments and thus produce the same NMR signal. Identifying chemically equivalent protons is crucial for predicting the number of unique signals in a spectrum. Protons are equivalent if they can be interchanged by a symmetry operation, such as rotation or reflection, without altering the molecule's structure.

Symmetry in Molecules

Symmetry in molecules plays a significant role in determining the number of unique NMR signals. Symmetrical molecules often have fewer unique signals because equivalent protons are indistinguishable in the NMR spectrum. Recognizing symmetry elements, such as planes of symmetry or axes of rotation, helps in identifying equivalent hydrogen atoms and predicting the NMR pattern.

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Related Practice

Textbook Question

How many sets of equivalent hydrogens are in each molecule shown?

(b)

Textbook Question

How many sets of equivalent hydrogens are in each molecule shown?

(c)

Textbook Question

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

(a)

Textbook Question

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

(b)

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.]

(a)

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

Key Concepts

¹H NMR Spectroscopy

Chemical Equivalence

Symmetry in Molecules

Watch next

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