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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Problem 48c

Textbook Question

Identify the important bands you would expect to find in an IR spectrum for the following molecules.
(c)

Verified step by step guidance

Identify the functional groups present in the molecule. Each functional group has characteristic absorption bands in an IR spectrum.

For each functional group, determine the typical wavenumber range where its absorption band appears. For example, O-H stretches are typically found around 3200-3600 cm^-1, C=O stretches around 1700 cm^-1, and C-H stretches around 2800-3000 cm^-1.

Consider the molecular structure to identify any specific interactions or conjugations that might shift the absorption bands. Conjugation can lower the frequency of C=O stretches, for instance.

Look for any unique or distinguishing features in the molecule that might lead to additional bands or shifts, such as hydrogen bonding, which can broaden and shift O-H stretches.

Compile a list of expected IR bands based on the identified functional groups and any structural considerations, noting the approximate wavenumber ranges for each.

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Key Concepts

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

Infrared (IR) Spectroscopy

Infrared spectroscopy is an analytical technique used to identify functional groups in molecules by measuring the absorption of infrared light at different wavelengths. Each functional group absorbs IR radiation at characteristic frequencies, producing a spectrum with peaks that correspond to specific bond vibrations. Understanding these absorption patterns is crucial for interpreting IR spectra.

Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties and reactivity. In IR spectroscopy, different functional groups absorb infrared light at distinct frequencies, allowing for their identification. For example, carbonyl groups (C=O) typically show strong absorption around 1700 cm⁻¹, while hydroxyl groups (O-H) exhibit broad peaks around 3200-3600 cm⁻¹.

Characteristic IR Absorption Bands

Characteristic IR absorption bands are specific regions in an IR spectrum where particular functional groups absorb infrared light. These bands are used to identify the presence of functional groups in a molecule. For instance, alkanes show C-H stretching vibrations around 2850-2960 cm⁻¹, while alkenes have C=C stretching near 1640-1680 cm⁻¹. Recognizing these bands is essential for analyzing and interpreting IR spectra.

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Related Practice

Textbook Question

How can IR spectroscopy be used to distinguish between the following compounds?

e. cyclohexene and cyclohexane

f. a primary amine and a tertiary amine

Textbook Question

How can IR spectroscopy be used to distinguish between the following compounds?

a. a ketone and an aldehyde

b. a cyclic ketone and an open-chain ketone

Textbook Question

A nitrogen-containing compound shows no absorption band at ~3400 cm^-1 and no absorption bands between ~1700 cm^-1 and ~1600 cm^-1 or between 2260 cm^-1 and 2220 cm^-1. What class of compound is it?

Textbook Question

Identify the important bands you would expect to find in an IR spectrum for the following molecules.

(a)

Textbook Question

A carboxylic acid can be converted to an ester using the conditions shown. Explain how a comparison of an IR spectrum of the reactant(s) and product can be used to determine whether the reaction was successful or not.

Textbook Question

Under acidic conditions, alkene A can be isomerized to the more stable alkene B. How could IR spectroscopy be used to distinguish between A and B? [There are a few correct answers.]

Textbook Question

The IR spectrum for anisole contains two C―O stretching bands in the fingerprint region. Match the band to the bond that gives rise to it. Why are these bands so intense?

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Textbook Question

How can you distinguish the following compounds using: a. their infrared spectra?

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