Question 1

Consider the following mass spectrum Which of the following compounds might have been used to produce this spectrum? A)C₆H₁₄ B)C₆H₁₂ C)C₆H₁₀ D)C₅H₁₂O

Accepted Answer

The answer of Consider the following mass spectrum  Which...

Question 2

Examining the infrared spectrum of a compound allows us to:
A)determine the types of functional groups present in the compound
B)determine the carbon-hydrogen framework of the compound
C)determine the molecular weight of the compound
D)determine the nature of the conjugated pi electron system in the compound

Accepted Answer

Infrared spectroscopy is a powerful tool for determining the presence of functional groups in a compound. It works by measuring the frequencies of infrared radiation absorbed by the compound, which correspond to the vibrations of functional groups. Each functional group has a unique set of vibrational frequencies, allowing for their identification in a compound. Therefore, option A is the most suitable choice as it correctly highlights the use of infrared spectra to determine the functional group in a compound.

Question 3

​When the molecular ion of 2,2-dimethylpentane fragments,the positive charge is most likely to stay on:
A)​the methyl group.
B)​the ethyl group.
C)​the propyl group.
D)​the tert-butyl group.

Accepted Answer

The tert-butyl group is the most stable carbocation due to the presence of three methyl groups, which provide significant electron density and stabilize the positive charge. Therefore, the positive charge is most likely to stay on the tert-butyl group when the molecular ion of 2,2-dimethylpentane fragments.

Question 4

Predict the m/z position of the parent peak,the peak due to dehydration of the alcohol and α-cleavage of the carbonyl in the mass spectrum of the compound shown below.

Accepted Answer

The answer of Predict the m/z position of the parent...

Question 5

Assume you are carrying out the conversion of 1-bromobutane to 1-butanol.How could you use IR spectroscopy to determine when the reaction is complete?

Accepted Answer

The answer of Assume you are carrying out the conversion...

Question 6

Exhibit 12-6 MATCH each of the following groups of bond-types to the region of the infrared spectrum in which their absorptions occur.Place the letter of the region in the blank to the left of the bond-type. -_____ N−H,C−H,and O−H stretching and bending motions. A)4000 to 2500 cm−¹ B)2500 to 2000 cm−¹ C)2000 to 1500 cm−¹ D)below 1500 cm−¹

Accepted Answer

N-H, C-H, and O-H bonds are associated with the functional groups of amines, alkanes, and alcohols, respectively. These bonds have stretching and bending motions that occur in the region of 4000 to 2500 cm-1.

Question 7

What m/z ratio would expect to find in the mass spectrum of the following compound due to dehydration? 
A)102
B)87
C)85
D)84
E)59

Accepted Answer

Dehydration typically results in the loss of a water molecule with a mass of 18 amu. Therefore, we would expect to see a peak in the mass spectrum that is 18 amu less than the molecular ion peak. The molecular ion peak in the provided spectrum is at m/z 102, so we would expect the dehydrated peak to be at 84 amu (102 - 18). Choice D is the only option that matches this expected peak.

Question 8

When 2-bromopropane reacts with ethoxide ion,two products are formed;one is the product of S_N2 substitution and the other is the product of E2 elimination.Write the structures of both products,and tell how they could be distinguished using IR spectroscopy.

Accepted Answer

The answer of When 2-bromopropane reacts with ethoxide ion,two products...

Question 9

Exhibit 12-6 MATCH each of the following groups of bond-types to the region of the infrared spectrum in which their absorptions occur.Place the letter of the region in the blank to the left of the bond-type. -_____ triple bond stretching vibrations. A)4000 to 2500 cm−¹ B)2500 to 2000 cm−¹ C)2000 to 1500 cm−¹ D)below 1500 cm−¹

Accepted Answer

Triple bond stretching vibrations typically occur in the region between 2500 to 2000 cm-1 in the infrared spectrum.

Question 10

Exhibit 12-6 MATCH each of the following groups of bond-types to the region of the infrared spectrum in which their absorptions occur.Place the letter of the region in the blank to the left of the bond-type. -_____ C=O,C=N,and C=C bond absorptions. A)4000 to 2500 cm−¹ B)2500 to 2000 cm−¹ C)2000 to 1500 cm−¹ D)below 1500 cm−¹

Accepted Answer

C=O, C=N, and C=C bond absorptions typically occur in the region of 2000 to 1500 cm^-1 in the infrared spectrum.

Question 11

Consider the following spectrum. The compound used to generate this spectrum might have which of the following molecular formulas? A)C₇H₁₆ B)C₇H₁₆O C)C₇H₁₄ D)C₇H₁₂ E)either c or d

Accepted Answer

Based on the spectrum, the compound contains one sulfur atom (S1), one hydrogen atom (H), and a carbon chain with 17 carbon atoms (C₇). The peak at around 1700 cm^-1 suggests the presence of a carbonyl group, which could be either a ketone or an aldehyde. The absence of a peak around 3400 cm^-1 suggests that there is no significant amount of a hydroxyl (-OH) group present. Therefore, the compound's molecular formula could be either C₇H₁₄ (with an aldehyde group) or C₇H₁₂ (with a ketone group). Therefore, the best choice would be E, either c or d.

Question 12

Which of the following regions of the IR spectrum would be significantly different for the following two substances? A)4000 - 2850 cm^-1 B)2850 - 2000 cm^-1 C)2000 - 1500 cm^-1 D)1500 - 400 cm^-1

Accepted Answer

The answer of Which of the following regions of the...

Question 13

In which of the following regions of the electromagnetic spectrum is the frequency lower than in the IR region?
A)radio wave
B)visible
C)ultraviolet
D)X ray

Accepted Answer

The electromagnetic spectrum is arranged in increasing order of frequency, with radio waves having the lowest frequencies and gamma rays having the highest frequencies. Therefore, radio waves have lower frequencies than the IR region, making option A the correct choice.

Question 14

Cyclohexene and 2-hexyne both have the molecular formula C₆H₁₀.How would you use infrared spectroscopy to distinguish between the two compounds?

Accepted Answer

The answer of Cyclohexene and 2-hexyne both have the molecular...

Question 15

Mass spectrometry and infrared spectroscopy are complementary techniques because:
A)Mass spectrometry provides information about the molar mass and formula while infrared spectroscopy helps identify the functional groups in the formula.
B)Infrared spectroscopy provides information about the molar mass and formula while mass spectrometry helps identify the functional groups in the formula.
C)Mass spectrometry provides information about the carbon-hydrogen framework while infrared spectroscopy helps identify the functional groups in the framework.
D)Infrared spectroscopy provides information about the carbon-hydrogen framework while mass spectrometry helps identify the functional groups in the framework.

Accepted Answer

Mass spectrometry measures the mass-to-charge ratio of ions present in a sample, allowing for the determination of the molar mass and formula of the compound. In contrast, infrared spectroscopy measures the absorption of infrared radiation by the functional groups present in the compound. Therefore, mass spectrometry provides information about the overall mass and formula of the compound, while infrared spectroscopy helps identify the specific functional groups present. Together, these techniques can provide a more complete understanding of the composition of a sample.

Question 16

Exhibit 12-6 MATCH each of the following groups of bond-types to the region of the infrared spectrum in which their absorptions occur.Place the letter of the region in the blank to the left of the bond-type. -_____ C−C,C−O,C−N,and C−X single-bond vibrations. A)4000 to 2500 cm−¹ B)2500 to 2000 cm−¹ C)2000 to 1500 cm−¹ D)below 1500 cm−¹

Accepted Answer

C−C, C−O, C−N, and C−X single-bond vibrations typically occur in the region below 1500 cm^−1 in the infrared spectrum. This region is known for fingerprint regions where complex vibrations occur, including those of single bonds.

Question 17

​What are the charged fragments produced if 4,5-dimethylhex-1-en-3-ol undergoes alpha cleavage?

Accepted Answer

The answer of ​What are the charged fragments produced if...

Question 18

Ethyl acetate and 2-butene-1,4-diol both have the molecular formula C₄H₈O₂.How would you use infrared spectroscopy to distinguish between the two?

Accepted Answer

The answer of ​Ethyl acetate and 2-butene-1,4-diol both have the...

Question 19

Which of the following provides information about the functional groups present in a sample?
A) 
B) 
C) 
D)

Accepted Answer

The answer of Which of the following provides information about...

Question 20

Which of the following regions of the electromagnetic spectrum would have insufficient energy to produce the following energy transition? 
A)radio wave
B)visible
C)ultraviolet
D)X ray

Accepted Answer

The energy transition referred to in the question requires a significant amount of energy. This energy is only available in the higher energy regions of the electromagnetic spectrum, such as ultraviolet and X-ray. Radio waves have much lower energy and would not be able to produce this energy transition.

Quiz 12: Structure Determination: Mass Spectrometry and Infrared Spectroscopy

Consider the following mass spectrum Which of the following compounds might have been used to produce this spectrum?

Examining the infrared spectrum of a compound allows us to:

​When the molecular ion of 2,2-dimethylpentane fragments,the positive charge is most likely to stay on:

Predict the m/z position of the parent peak,the peak due to dehydration of the alcohol and α-cleavage of the carbonyl in the mass spectrum of the compound shown below.

Assume you are carrying out the conversion of 1-bromobutane to 1-butanol.How could you use IR spectroscopy to determine when the reaction is complete?

Exhibit 12-6 MATCH each of the following groups of bond-types to the region of the infrared spectrum in which their absorptions occur.Place the letter of the region in the blank to the left of the bond-type. -_____ N−H,C−H,and O−H stretching and bending motions.

What m/z ratio would expect to find in the mass spectrum of the following compound due to dehydration?

When 2-bromopropane reacts with ethoxide ion,two products are formed;one is the product of SN2 substitution and the other is the product of E2 elimination.Write the structures of both products,and tell how they could be distinguished using IR spectroscopy.

Exhibit 12-6 MATCH each of the following groups of bond-types to the region of the infrared spectrum in which their absorptions occur.Place the letter of the region in the blank to the left of the bond-type. -_____ triple bond stretching vibrations.

Exhibit 12-6 MATCH each of the following groups of bond-types to the region of the infrared spectrum in which their absorptions occur.Place the letter of the region in the blank to the left of the bond-type. -_____ C=O,C=N,and C=C bond absorptions.

Consider the following spectrum. The compound used to generate this spectrum might have which of the following molecular formulas?

Which of the following regions of the IR spectrum would be significantly different for the following two substances?

In which of the following regions of the electromagnetic spectrum is the frequency lower than in the IR region?

Cyclohexene and 2-hexyne both have the molecular formula C6H10.How would you use infrared spectroscopy to distinguish between the two compounds?

Mass spectrometry and infrared spectroscopy are complementary techniques because:

Exhibit 12-6 MATCH each of the following groups of bond-types to the region of the infrared spectrum in which their absorptions occur.Place the letter of the region in the blank to the left of the bond-type. -_____ C−C,C−O,C−N,and C−X single-bond vibrations.

​What are the charged fragments produced if 4,5-dimethylhex-1-en-3-ol undergoes alpha cleavage?

​Ethyl acetate and 2-butene-1,4-diol both have the molecular formula C4H8O2.How would you use infrared spectroscopy to distinguish between the two?

Which of the following provides information about the functional groups present in a sample?

Which of the following regions of the electromagnetic spectrum would have insufficient energy to produce the following energy transition?

When the molecular ion of 2,2-dimethylpentane fragments,the positive charge is most likely to stay on:

When 2-bromopropane reacts with ethoxide ion,two products are formed;one is the product of S_N2 substitution and the other is the product of E2 elimination.Write the structures of both products,and tell how they could be distinguished using IR spectroscopy.

Cyclohexene and 2-hexyne both have the molecular formula C₆H₁₀.How would you use infrared spectroscopy to distinguish between the two compounds?

What are the charged fragments produced if 4,5-dimethylhex-1-en-3-ol undergoes alpha cleavage?

Ethyl acetate and 2-butene-1,4-diol both have the molecular formula C₄H₈O₂.How would you use infrared spectroscopy to distinguish between the two?