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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Problem 42

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?

Verified step by step guidance

Identify the structure of hexane, which is a linear alkane with the molecular formula C₆H₁₄. It consists of a chain of six carbon atoms with hydrogen atoms filling the remaining valences.

Locate the positions Hₐ and H₆ in the hexane molecule. These are typically the terminal hydrogen atoms on the first and last carbon atoms in the chain.

Replace the hydrogen atom Hₐ on the first carbon with a deuterium atom (D), resulting in a new molecule: C₆H₁₃D. Similarly, replace the hydrogen atom H₆ on the last carbon with a deuterium atom, resulting in another molecule: C₆H₁₃D.

Determine the relationship between the two deuterated products. Since hexane is a symmetrical molecule, replacing Hₐ or H₆ with deuterium results in identical molecules. Therefore, the two products are identical and are considered to be the same compound.

Analyze the ¹H NMR spectrum implications. Since the two hydrogens (Hₐ and H₆) are in equivalent positions in a symmetrical molecule, they are chemically equivalent. Thus, they would give rise to a single signal in the ¹H NMR spectrum.

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Key Concepts

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

Isotopic Substitution

Isotopic substitution involves replacing an atom in a molecule with one of its isotopes, such as replacing hydrogen (H) with deuterium (D), a heavier isotope of hydrogen. This substitution can affect the physical and chemical properties of the molecule, including its behavior in spectroscopic analysis, due to the difference in mass and nuclear properties between the isotopes.

Stereochemistry and Chirality

Stereochemistry refers to the spatial arrangement of atoms in molecules and its impact on their chemical behavior. In the context of hexane, replacing two hydrogens with deuterium can create stereoisomers if the replacements occur at chiral centers. These stereoisomers, known as enantiomers or diastereomers, can have different physical properties and may lead to different NMR signals.

¹H NMR Spectroscopy

¹H NMR spectroscopy is a technique used to determine the structure of organic compounds by observing the magnetic environment of hydrogen atoms. In NMR, chemically equivalent hydrogens produce a single signal, while non-equivalent hydrogens produce separate signals. The replacement of hydrogens with deuterium can alter the equivalence of hydrogens, potentially leading to changes in the number of signals observed in the 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?

(b)

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

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)

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)

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