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

Infrared Spectroscopy Table

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

Infrared Spectroscopy Table

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5:22 minutes

Problem 67e,f

Textbook Question

Give approximate wavenumbers for the major characteristic IR absorption bands that would be given by each of the following compounds:
e.
f.

Verified step by step guidance

Identify the functional groups present in each compound. Infrared (IR) spectroscopy detects vibrations of bonds, and each functional group has characteristic absorption bands.

For each functional group, determine the approximate wavenumber range where its characteristic absorption band appears. For example, O-H stretching appears around 3200-3600 cm⁻¹, C=O stretching appears around 1650-1750 cm⁻¹, and C-H stretching appears around 2800-3100 cm⁻¹.

Consider the molecular structure of each compound to identify any additional features that might shift or influence the absorption bands, such as conjugation, hydrogen bonding, or ring strain.

List the major characteristic absorption bands for each compound, specifying the approximate wavenumber ranges for each functional group identified.

Ensure that the wavenumber ranges provided are approximate and account for any potential variations due to the specific environment of the functional groups in the compounds.

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Key Concepts

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

Infrared Spectroscopy (IR)

Infrared spectroscopy is a technique used to identify molecular structures by measuring the absorption of infrared light by a compound. Different functional groups absorb IR radiation at specific wavenumbers, allowing chemists to deduce the presence of certain bonds or groups in a molecule. Understanding the basic principles of IR spectroscopy is essential for interpreting the absorption bands associated with various compounds.

Wavenumber

Wavenumber is a unit of measurement used in spectroscopy, defined as the number of waves per unit distance, typically expressed in cm⁻¹. It is inversely related to wavelength and directly correlates with energy; higher wavenumbers correspond to higher energy transitions. In IR spectroscopy, wavenumbers are used to identify specific vibrational modes of molecular bonds, making it crucial for analyzing absorption bands.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Each functional group has a unique set of IR absorption bands associated with its vibrational modes. Recognizing common functional groups, such as alcohols, carbonyls, and amines, is vital for predicting the IR absorption patterns of compounds and interpreting their spectra.

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Related Practice

Textbook Question

Predict the characteristic infrared absorptions of the functional groups in the following molecules.

(d) pent-1-yne

(e) diethylamine

(f) pentanoic acid

Textbook Question

Predict the characteristic infrared absorptions of the functional groups in the following molecules.

(a) cyclohexene

(b) pentan-2-ol

Textbook Question

These five structures all have distinguishing absorptions in the IR. Match each structure with its characteristic absorption.

(a) sharp, 2254 cm^–1

(b) very broad, centered about 3330 cm^–1

(d) broad with spikes at 3367 and 3292 cm^–1

(e) strong, sharp 1717 cm^–1

Textbook Question

Three common lab experiments are shown. In each case, describe how the IR spectrum of the product would differ from that of the reactant. Give approximate frequencies for distinctive peaks in the IR spectrum of the reactant and also that of the product.

Textbook Question

For each of the following pairs of compounds, name one absorption band that can be used to distinguish between them.

Textbook Question

Norlutin and Enovid are ketones that suppress ovulation, so they have been used clinically as contraceptives. For which of these compounds would you expect the infrared carbonyl absorption (C=O stretch) to be at a higher frequency? Explain.

Textbook Question

Give approximate wavenumbers for the major characteristic IR absorption bands that would be given by each of the following compounds:

Textbook Question

Rank the following compounds from highest wavenumber to lowest wavenumber for their C-O absorption band:

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Give approximate wavenumbers for the major characteristic IR absorption bands that would be given by each of the following compounds: e. f.

Key Concepts

Infrared Spectroscopy (IR)

Wavenumber

Functional Groups

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Give approximate wavenumbers for the major characteristic IR absorption bands that would be given by each of the following compounds:
e.
f.