Which choice best explains why the molecules below can be distinguished by IR. H Molecule A O Molecule A has a peak just above 3000 cm-1 and Molecule B does not. Molecule A has a peak for an aldehyde around 2200 cm and Molecule B does not. -1 Molecule B has a carbonyl peak around 1750 cm1 and Molecule A does not. Molecule A and Molecule B can't be easily distinguished by IR. OOOO .CH3 Molecule B
Which choice best explains why the molecules below can be distinguished by IR. H Molecule A O Molecule A has a peak just above 3000 cm-1 and Molecule B does not. Molecule A has a peak for an aldehyde around 2200 cm and Molecule B does not. -1 Molecule B has a carbonyl peak around 1750 cm1 and Molecule A does not. Molecule A and Molecule B can't be easily distinguished by IR. OOOO .CH3 Molecule B
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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- **Molecule A:** Contains a benzene ring with an aldehyde functional group.
- **Molecule B:** Contains a benzene ring with an acetyl group (a ketone substituted with a methyl group).
### Multiple Choice Explanation:
1. **Molecule A has a peak just above 3000 cm⁻¹ and Molecule B does not.**
2. **Molecule A has a peak for an aldehyde around 2200 cm⁻¹ and Molecule B does not.**
3. **Molecule B has a carbonyl peak around 1750 cm⁻¹ and Molecule A does not.**
4. **Molecule A and Molecule B can't be easily distinguished by IR.**
### Correct Answer:
**Molecule B has a carbonyl peak around 1750 cm⁻¹ and Molecule A does not.**
#### Explanation:
Infrared (IR) spectroscopy is a powerful technique used to identify certain functional groups based on their characteristic absorption bands. Molecule A (which contains an aldehyde) and Molecule B (which contains a ketone) can be distinguished based on the specific absorption frequencies characteristic to these groups.
- **Aldehyde (Molecule A)**: Typically shows a distinctive absorption around 1725 cm⁻¹ corresponding to the C=O stretch of the aldehyde.
- **Ketone (Molecule B)**: Typically shows a strong absorption around 1705-1750 cm⁻¹ for the carbonyl (C=O) stretch.
Thus, **option 3** correctly identifies that Molecule B has a carbonyl peak around 1750 cm⁻¹, which Molecule A does not have, allowing easy distinction using IR spectroscopy.
### Note:
IR spectroscopy peaks are critical for identifying different functional groups in chemical molecules, making it an essential tool in molecular analysis in organic chemistry.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F5bc418ab-5051-450d-ba5a-1e906e0fb9c9%2Fddc37c93-49ed-436a-94e5-1d195ac907aa%2Fn0mm7ib_processed.jpeg&w=3840&q=75)
Transcribed Image Text:**Infrared Spectroscopy: Distinguishing Molecules**
### Which choice best explains why the molecules below can be distinguished by IR?

- **Molecule A:** Contains a benzene ring with an aldehyde functional group.
- **Molecule B:** Contains a benzene ring with an acetyl group (a ketone substituted with a methyl group).
### Multiple Choice Explanation:
1. **Molecule A has a peak just above 3000 cm⁻¹ and Molecule B does not.**
2. **Molecule A has a peak for an aldehyde around 2200 cm⁻¹ and Molecule B does not.**
3. **Molecule B has a carbonyl peak around 1750 cm⁻¹ and Molecule A does not.**
4. **Molecule A and Molecule B can't be easily distinguished by IR.**
### Correct Answer:
**Molecule B has a carbonyl peak around 1750 cm⁻¹ and Molecule A does not.**
#### Explanation:
Infrared (IR) spectroscopy is a powerful technique used to identify certain functional groups based on their characteristic absorption bands. Molecule A (which contains an aldehyde) and Molecule B (which contains a ketone) can be distinguished based on the specific absorption frequencies characteristic to these groups.
- **Aldehyde (Molecule A)**: Typically shows a distinctive absorption around 1725 cm⁻¹ corresponding to the C=O stretch of the aldehyde.
- **Ketone (Molecule B)**: Typically shows a strong absorption around 1705-1750 cm⁻¹ for the carbonyl (C=O) stretch.
Thus, **option 3** correctly identifies that Molecule B has a carbonyl peak around 1750 cm⁻¹, which Molecule A does not have, allowing easy distinction using IR spectroscopy.
### Note:
IR spectroscopy peaks are critical for identifying different functional groups in chemical molecules, making it an essential tool in molecular analysis in organic chemistry.
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