It is to be explained why IR spectroscopy does not distinguish very well between isomers I and J. It is to be explained how UV-vis spectroscopy could be used to distinguish between them. Concept introduction: In UV-vis spectroscopy, absorption of a photon promotes an electron from a lower-energy MO to a higher-energy MO. The λ max for the longest-wavelength absorption in the spectrum corresponds to the HOMO-LUMO. Conjugation decreases the energy difference between the HOMO-LUMO and thus increases the wavelength of the photon absorbed. IR spectroscopy enables to identify different functional groups in the given molecule. One of the greatest advantages of IR spectroscopy is that the frequency of a particular type of vibration is typically found within a characteristic range of frequencies, regardless of the functional group with which the vibration is associated. The fact that absorptions by certain vibrations appear with characteristic frequency ranges enables us to use IR spectroscopy to obtain structural information about a molecule.

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Chapter 15, Problem 15.57P

Interpretation Introduction

Interpretation:

It is to be explained why IR spectroscopy does not distinguish very well between isomers I and J. It is to be explained how UV-vis spectroscopy could be used to distinguish between them.

Concept introduction:

In UV-vis spectroscopy, absorption of a photon promotes an electron from a lower-energy MO to a higher-energy MO. The λmax for the longest-wavelength absorption in the spectrum corresponds to the HOMO-LUMO. Conjugation decreases the energy difference between the HOMO-LUMO and thus increases the wavelength of the photon absorbed.

IR spectroscopy enables to identify different functional groups in the given molecule.

One of the greatest advantages of IR spectroscopy is that the frequency of a particular type of vibration is typically found within a characteristic range of frequencies, regardless of the functional group with which the vibration is associated. The fact that absorptions by certain vibrations appear with characteristic frequency ranges enables us to use IR spectroscopy to obtain structural information about a molecule.

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I have a question about this problem involving mechanisms and drawing curved arrows for acids and bases. I know we need to identify the nucleophile and electrophile, but are there different types of reactions? For instance, what about Grignard reagents and other types that I might not be familiar with? Can you help me with this? I want to identify the names of the mechanisms for problems 1-14, such as Gilman reagents and others. Are they all the same? Also, could you rewrite it so I can better understand? The handwriting is pretty cluttered. Additionally, I need to label the nucleophile and electrophile, but my main concern is whether those reactions differ, like the "Brønsted-Lowry acid-base mechanism, Lewis acid-base mechanism, acid-catalyzed mechanisms, acid-catalyzed reactions, base-catalyzed reactions, nucleophilic substitution mechanisms (SN1 and SN2), elimination reactions (E1 and E2), organometallic mechanisms, and so forth."