Question 1

Describe the similarities and differences in the infrared spectra of methyl propanoate and butanoic acid.

Accepted Answer

The answer of Describe the similarities and differences in the...

Question 2

Which of the following compounds absorbs the longest wavelength of UV-visible light?

Accepted Answer

The compound with the longest conjugation system will absorb light of the longest wavelength. (E)-1,3,5-hexatriene has six carbons participating in conjugation, making it the compound with the longest conjugation system in the list. Therefore, (E)-1,3,5-hexatriene absorbs the longest wavelength of UV-visible light.

Question 3

Deduce a possible structure for the compound with the IR absorptions below. C₃H₃Br: 3300,2900,2100 cm^-1

Accepted Answer

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Question 4

Deduce a possible structure for the compound with the IR absorptions below. C₅H₈O: 3000,1750 cm^-1

Accepted Answer

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Question 5

Is the λ_max of phenol in aqueous solution affected by the pH of the solution? If so,explain how and why λ_max changes.

Accepted Answer

The answer of Is the λ_max of phenol in aqueous...

Question 6

How could IR spectroscopy be used to distinguish between the following pair of compounds? HOCH₂CH₂CHO and CH₃CH₂CO₂H

Accepted Answer

The answer of How could IR spectroscopy be used to...

Question 7

How could IR spectroscopy be used to distinguish between the following pair of compounds? CH₃OCH₂CH₃ and CH₃CH₂CH₂OH

Accepted Answer

The answer of How could IR spectroscopy be used to...

Question 8

Which of the following compounds exhibits the highest λ_max in UV spectra?

Accepted Answer

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Question 9

Identify the compound that has a formula of C₃H₆O with a stretching vibration at 1050 cm^-1 and an absorption band at 3400 cm^-1,but no doublet at 1380 cm^-1.

Accepted Answer

The compound is 1-propanol, which has an -OH group causing the absorption band at 3400 cm⁻¹ and a C-O stretching vibration around 1050 cm⁻¹. The absence of a doublet at 1380 cm⁻¹ indicates it is not a secondary alcohol like 2-propanol.

Question 10

Deduce a possible structure for the compound with the IR absorptions below. C₃H₅N: 3000,2250 cm^-1

Accepted Answer

The answer of Deduce a possible structure for the compound...

Question 11

A mixture of two compounds give absorption bands at 1470,1595,1700,2720,and 2740 cm^-1.What compounds are present?

Accepted Answer

The absorption bands at 2720 and 2740 cm^-1 are characteristic of aldehydes, while the bands at 1470 and 1595 cm^-1 are indicative of benzene. The band at 1700 cm^-1 is consistent with a carbonyl group, which is present in aldehydes.

Question 12

Identify the compound that has a formula of C₄H₉N and has one absorption band at 3400 cm^-1 and a doublet at 1380 cm^-1.

Accepted Answer

The presence of an absorption band at 3400 cm^-1 and a doublet at 1380 cm^-1 suggests the presence of an amine group in the compound. Among the given choices, only C contains an amine group (methyl and isopropyl groups attached to nitrogen). None of the other choices have amine groups.

Question 13

In the infrared spectrum,a compound of formula C₄H₈O gave an absorption band at 1720 cm^-1,but no bands at 2720 - 2830 and 3400 cm^-1.What is the compound?

Accepted Answer

The absorption band at 1720 cm-1 corresponds to the carbonyl group in a ketone or aldehyde compound. The absence of absorption bands at 2720 - 2830 cm-1 and 3400 cm-1 indicates the absence of C-H stretching in an aldehyde compound or O-H stretching in an alcohol compound. Among the options, 2-butanone (choice A) fits this description, as it has a carbonyl group but no C-H or O-H stretching bands in the specified region of the infrared spectrum. Therefore, choice A is the best answer.

Question 14

An increase in conjugation is correlated with ________ in the energy of the LUMO,________ in the energy of the HOMO,and ________ in l_max.

Accepted Answer

An increase in conjugation usually results in a redshift of the absorption spectrum, which means a decrease in the energy of the LUMO and an increase in the energy of the HOMO. Additionally, an increase in conjugation often leads to an increase in the maximum intensity of the S1U1B0 transition (i.e., the maximum absorption peak in the UV-Vis spectrum). Therefore, the correct answer is B, where there is a decrease in the energy of the LUMO, an increase in the energy of the HOMO, and an increase in the maximum intensity of the S1U1B0 transition.

Question 15

Which molecule below has two significant bands in the IR at 2720 cm^-1 and 2820 cm^-1(medium)?

Accepted Answer

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Question 16

Which of the following methods is most suitable for studying conjugation in molecules?

Accepted Answer

UV-visible spectroscopy is well suited for studying conjugation in molecules as it involves the absorption of light in the UV-visible region by the π-electrons present in the conjugated system. This absorption leads to a characteristic pattern of peaks in the UV-visible spectrum that can be used to determine the extent and nature of conjugation in the molecule.

Question 17

Which molecule below has a significant band in the IR at 3300 cm^-1 (medium and sharp)?

Accepted Answer

The significant band in the IR at 3300 cm-1 indicates the presence of a C-H bond. Among the given molecules, 1-pentyne (D) is the only one with a C≡C-H bond, which exhibits a strong infrared absorption at around 3300 cm-1.

Question 18

Deduce a possible structure for the compound with the IR absorptions below. C₄H₈O: 3000,2800,2715,1715 cm^-1

Accepted Answer

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Question 19

In the UV-visible spectrum of (E)-1,3,5-hexatriene,the lowest energy absorption corresponds to

Accepted Answer

The lowest energy absorption in (E)-1,3,5-hexatriene corresponds to a π to π* transition because it involves the excitation of an electron from a π bonding orbital to a π* antibonding orbital. This is a common type of transition in conjugated systems like hexatriene.

Question 20

Absorption of UV-visible energy by a molecule results in

Accepted Answer

Absorption of UV-visible energy by a molecule results in electronic transitions, as these energies are in the range required to excite electrons from lower energy orbitals to higher energy ones. Vibrational and rotational transitions require lower energy radiation, such as infrared radiation. Nuclear transitions are much higher in energy and require ionizing radiation, such as x-rays or gamma rays.

Quiz 13: Mass Spectrometry,infrared Spectroscopy,and Uvvis Spectroscopy

Describe the similarities and differences in the infrared spectra of methyl propanoate and butanoic acid.

Which of the following compounds absorbs the longest wavelength of UV-visible light?

Deduce a possible structure for the compound with the IR absorptions below. C₃H₃Br: 3300,2900,2100 cm^-1

Deduce a possible structure for the compound with the IR absorptions below. C₅H₈O: 3000,1750 cm^-1

Is the λ_max of phenol in aqueous solution affected by the pH of the solution? If so,explain how and why λ_max changes.

How could IR spectroscopy be used to distinguish between the following pair of compounds? HOCH₂CH₂CHO and CH₃CH₂CO₂H

How could IR spectroscopy be used to distinguish between the following pair of compounds? CH₃OCH₂CH₃ and CH₃CH₂CH₂OH

Which of the following compounds exhibits the highest λ_max in UV spectra?

Identify the compound that has a formula of C₃H₆O with a stretching vibration at 1050 cm^-1 and an absorption band at 3400 cm^-1,but no doublet at 1380 cm^-1.

Deduce a possible structure for the compound with the IR absorptions below. C₃H₅N: 3000,2250 cm^-1

A mixture of two compounds give absorption bands at 1470,1595,1700,2720,and 2740 cm^-1.What compounds are present?

Identify the compound that has a formula of C₄H₉N and has one absorption band at 3400 cm^-1 and a doublet at 1380 cm^-1.

In the infrared spectrum,a compound of formula C₄H₈O gave an absorption band at 1720 cm^-1,but no bands at 2720 - 2830 and 3400 cm^-1.What is the compound?

An increase in conjugation is correlated with in the energy of the LUMO, in the energy of the HOMO,and in l_max.

Which molecule below has two significant bands in the IR at 2720 cm^-1 and 2820 cm^-1(medium) ?

Which of the following methods is most suitable for studying conjugation in molecules?

Which molecule below has a significant band in the IR at 3300 cm^-1 (medium and sharp) ?

Deduce a possible structure for the compound with the IR absorptions below. C₄H₈O: 3000,2800,2715,1715 cm^-1

In the UV-visible spectrum of (E) -1,3,5-hexatriene,the lowest energy absorption corresponds to

Absorption of UV-visible energy by a molecule results in

Quiz 13: Mass Spectrometry,infrared Spectroscopy,and Uvvis Spectroscopy

Describe the similarities and differences in the infrared spectra of methyl propanoate and butanoic acid.

Which of the following compounds absorbs the longest wavelength of UV-visible light?

Deduce a possible structure for the compound with the IR absorptions below. C3H3Br: 3300,2900,2100 cm-1

Deduce a possible structure for the compound with the IR absorptions below. C5H8O: 3000,1750 cm-1

Is the λmax of phenol in aqueous solution affected by the pH of the solution? If so,explain how and why λmax changes.

How could IR spectroscopy be used to distinguish between the following pair of compounds? HOCH2CH2CHO and CH3CH2CO2H

How could IR spectroscopy be used to distinguish between the following pair of compounds? CH3OCH2CH3 and CH3CH2CH2OH

Which of the following compounds exhibits the highest λmax in UV spectra?

Identify the compound that has a formula of C3H6O with a stretching vibration at 1050 cm-1 and an absorption band at 3400 cm-1,but no doublet at 1380 cm-1.

Deduce a possible structure for the compound with the IR absorptions below. C3H5N: 3000,2250 cm-1

A mixture of two compounds give absorption bands at 1470,1595,1700,2720,and 2740 cm-1.What compounds are present?

Identify the compound that has a formula of C4H9N and has one absorption band at 3400 cm-1 and a doublet at 1380 cm-1.

In the infrared spectrum,a compound of formula C4H8O gave an absorption band at 1720 cm-1,but no bands at 2720 - 2830 and 3400 cm-1.What is the compound?

An increase in conjugation is correlated with ________ in the energy of the LUMO,________ in the energy of the HOMO,and ________ in lmax.

Which molecule below has two significant bands in the IR at 2720 cm-1 and 2820 cm-1 (medium) ?

Which of the following methods is most suitable for studying conjugation in molecules?

Which molecule below has a significant band in the IR at 3300 cm-1 (medium and sharp) ?

Deduce a possible structure for the compound with the IR absorptions below. C4H8O: 3000,2800,2715,1715 cm-1

In the UV-visible spectrum of (E) -1,3,5-hexatriene,the lowest energy absorption corresponds to

Absorption of UV-visible energy by a molecule results in

Deduce a possible structure for the compound with the IR absorptions below. C₃H₃Br: 3300,2900,2100 cm^-1

Deduce a possible structure for the compound with the IR absorptions below. C₅H₈O: 3000,1750 cm^-1

Is the λ_max of phenol in aqueous solution affected by the pH of the solution? If so,explain how and why λ_max changes.

How could IR spectroscopy be used to distinguish between the following pair of compounds? HOCH₂CH₂CHO and CH₃CH₂CO₂H

How could IR spectroscopy be used to distinguish between the following pair of compounds? CH₃OCH₂CH₃ and CH₃CH₂CH₂OH

Which of the following compounds exhibits the highest λ_max in UV spectra?

Identify the compound that has a formula of C₃H₆O with a stretching vibration at 1050 cm^-1 and an absorption band at 3400 cm^-1,but no doublet at 1380 cm^-1.

Deduce a possible structure for the compound with the IR absorptions below. C₃H₅N: 3000,2250 cm^-1

A mixture of two compounds give absorption bands at 1470,1595,1700,2720,and 2740 cm^-1.What compounds are present?

Identify the compound that has a formula of C₄H₉N and has one absorption band at 3400 cm^-1 and a doublet at 1380 cm^-1.

In the infrared spectrum,a compound of formula C₄H₈O gave an absorption band at 1720 cm^-1,but no bands at 2720 - 2830 and 3400 cm^-1.What is the compound?

An increase in conjugation is correlated with in the energy of the LUMO, in the energy of the HOMO,and in l_max.

Which molecule below has two significant bands in the IR at 2720 cm^-1 and 2820 cm^-1(medium) ?

Which molecule below has a significant band in the IR at 3300 cm^-1 (medium and sharp) ?

Deduce a possible structure for the compound with the IR absorptions below. C₄H₈O: 3000,2800,2715,1715 cm^-1