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

H NMR Table

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

H NMR Table

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5:35 minutes

Problem 14h

Textbook Question

Without referring to Table 14.1, label the proton or set of protons in each compound that gives the signal at the lowest frequency a, at the next lowest b, and so on.
h.

Verified step by step guidance

Step 1: Analyze the structure of the molecule provided. The molecule contains a bromine atom attached to a CH2 group, which is connected to another CH2 group bonded to an oxygen atom. The oxygen atom is further bonded to a methyl group (CH3).

Step 2: Understand the concept of chemical shift in NMR spectroscopy. Protons in different chemical environments resonate at different frequencies due to the electronic environment around them. Electronegative atoms like bromine and oxygen deshield nearby protons, causing them to resonate at higher frequencies.

Step 3: Identify the protons in the molecule. There are three sets of protons: (1) the CH2 group attached to bromine, (2) the CH2 group attached to oxygen, and (3) the CH3 group attached to oxygen.

Step 4: Determine the relative chemical shifts. The CH2 group attached to bromine will resonate at the highest frequency due to the strong deshielding effect of bromine. The CH2 group attached to oxygen will resonate at the next highest frequency due to the deshielding effect of oxygen. The CH3 group attached to oxygen will resonate at the lowest frequency because it is less deshielded compared to the other groups.

Step 5: Assign labels based on frequency. Label the CH3 protons as 'a' (lowest frequency), the CH2 protons attached to oxygen as 'b' (next lowest frequency), and the CH2 protons attached to bromine as 'c' (highest frequency).

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Key Concepts

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

Chemical Shift in NMR Spectroscopy

In nuclear magnetic resonance (NMR) spectroscopy, the chemical shift refers to the resonance frequency of a nucleus relative to a standard in a magnetic field. It is influenced by the electronic environment surrounding the nucleus, with protons in electron-rich environments appearing at higher frequencies (lower ppm values) and those in electron-poor environments at lower frequencies (higher ppm values). Understanding chemical shifts is crucial for identifying the types of protons present in a compound.

Electronegativity and Inductive Effect

Electronegativity is the tendency of an atom to attract electrons towards itself. In organic compounds, electronegative atoms (like Br or O) can withdraw electron density from nearby protons, affecting their chemical shift in NMR. This inductive effect can lead to downfield shifts (lower frequency) for protons adjacent to electronegative atoms, making it essential to consider when analyzing NMR spectra.

Integration and Multiplicity in NMR

Integration in NMR spectroscopy refers to the area under the peaks in the spectrum, which correlates to the number of protons contributing to that signal. Multiplicity indicates the splitting of NMR signals due to neighboring protons, following the n+1 rule, where n is the number of adjacent protons. Understanding these concepts helps in determining the number of protons and their environments, which is vital for interpreting the NMR data accurately.

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Related Practice

Textbook Question

Predict the approximate chemical shifts of the protons in the following compounds.

(d) CH₃CH₂–C≡C–H

Textbook Question

The NMR spectrum of toluene (methylbenzene) was shown in Figure 13-11.

<IMAGE>

(a) How many different kinds of protons are there in toluene?

(b) Explain why the aromatic region around d7.2 is broad, with more than one sharp absorption.

Textbook Question

Predict the chemical shifts of the protons in the following compounds.

(a)

(b)

Textbook Question

In a 300-MHz spectrometer, the protons in iodomethane absorb at a position 650 Hz downfield from TMS.

(a) What is the chemical shift of these protons?

(b) What is the chemical shift of the iodomethane protons in a 60-MHz spectrometer?

Textbook Question

Without referring to Table 14.1, label the proton or set of protons in each compound that gives the signal at the lowest frequency a, at the next lowest b, and so on.

Textbook Question

Label each set of chemically equivalent protons, using a for the set that will be at the lowest frequency in the ¹H NMR spectrum, b for the next lowest, and so on. Indicate the multiplicity of each signal.

Textbook Question

Explain the relative chemical shifts of the benzene ring protons in Figure 14.18.

<IMAGE>

Textbook Question

Without referring to Table 14.1, label the proton or set of protons in each compound that gives the signal at the lowest frequency a, at the next lowest b, and so on.

c. ClCH₂CH₂CH₂Cl

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Without referring to Table 14.1, label the proton or set of protons in each compound that gives the signal at the lowest frequency a, at the next lowest b, and so on. h.

Key Concepts

Chemical Shift in NMR Spectroscopy

Electronegativity and Inductive Effect

Integration and Multiplicity in NMR

Watch next

Without referring to Table 14.1, label the proton or set of protons in each compound that gives the signal at the lowest frequency a, at the next lowest b, and so on.
h.