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 51

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.

Verified step by step guidance

Identify the functional groups present in the reactant (carboxylic acid) and the product (ester). Carboxylic acids have a characteristic C=O stretch around 1700 cm^-1 and an O-H stretch around 2500-3300 cm^-1 in their IR spectrum.

Recognize that esters have a C=O stretch similar to carboxylic acids, but they lack the broad O-H stretch. Instead, esters show a C-O stretch typically in the range of 1050-1300 cm^-1.

Compare the IR spectrum of the reactant with that of the product. Look for the disappearance of the broad O-H stretch in the product's spectrum, which indicates the loss of the carboxylic acid's hydroxyl group.

Check for the presence of the ester C-O stretch in the product's IR spectrum, which should appear as a new peak compared to the reactant's spectrum.

Conclude that the reaction was successful if the IR spectrum of the product shows the disappearance of the O-H stretch and the appearance of the C-O stretch, confirming the conversion of the carboxylic acid to an ester.

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Key Concepts

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

Carboxylic Acid to Ester Conversion

The conversion of a carboxylic acid to an ester typically involves a reaction with an alcohol in the presence of an acid catalyst, known as esterification. This process replaces the hydroxyl group (-OH) of the carboxylic acid with an alkoxy group (-OR) from the alcohol, forming an ester and water as byproducts.

Infrared (IR) Spectroscopy

IR spectroscopy is a technique used to identify functional groups in organic compounds by measuring the absorption of infrared light. Different functional groups absorb specific frequencies, creating a spectrum that can be analyzed to determine the presence or absence of particular bonds, such as the carbonyl group in carboxylic acids and esters.

Functional Group Identification via IR Spectrum

In the IR spectrum, carboxylic acids show a broad O-H stretch around 2500-3000 cm⁻¹ and a sharp C=O stretch near 1700 cm⁻¹. Esters, however, lack the O-H stretch and exhibit a C=O stretch around 1735-1750 cm⁻¹. Comparing these spectra allows one to confirm the conversion by the disappearance of the O-H stretch and the shift in the C=O stretch.

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Related Practice

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

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

(c)

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?

Textbook Question

The acid-catalyzed hydrolysis of an ester results in the formation of an equal amount of carboxylic acid and alcohol.

(b) Once separated, how could you distinguish between the carboxylic acid and alcohol using IR spectroscopy?

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