Question 1

Which of the following will produce (M+2)⁺ • peak one third the intensity of M⁺• peak?

Accepted Answer

The answer of Which of the following will produce (M+2)⁺...

Question 2

Provide a molecular formula that is consistent with the following mass spectral data. M⁺•at m/z = 136, relative height = 65.6% (M+1)⁺ •at m/z = 137, relative height = 6.2%

Accepted Answer

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Question 3

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 72, relative height = 73.0% (M+1)⁺•at m/z = 73, relative height = 3.3%

Accepted Answer

The molecular formula consistent with the mass spectral data showing a base peak at m/z = 72 and a (M+1) peak at m/z = 73 is C6H12O. This corresponds to choice D, as it is the only option with a molecular formula that matches the given mass spectral data, indicating the presence of carbon (C), hydrogen (H), and oxygen (O) in the specified amounts.

Question 4

For which of the following compounds will the (M+2)⁺• peak intensity be around one third the intensity of the molecular ion peak?

Accepted Answer

The (M+2)⁺• peak corresponds to the ion that is formed when one of the isotopes of the molecule (usually 13C) is present instead of the regular isotope. This results in an increase of two mass units compared to the molecular ion. The intensity of this peak is proportional to the abundance of the isotope in the sample. Since chlorine has two isotopes (35Cl and 37Cl) with a natural abundance ratio of approximately 3:1, the (M+2)⁺• peak intensity for a molecule containing chlorine will be around one third of the molecular ion peak intensity. Therefore, option C, which contains chlorine, is the correct choice.

Question 5

For which of the following compounds will the (M+2)⁺• peak intensity be equal to the intensity of the molecular ion peak?

Accepted Answer

Bromine has two isotopes, Br-79 and Br-81, with nearly equal natural abundance, resulting in an (M+2) peak with intensity equal to the molecular ion peak.

Question 6

Which of the following m/z values corresponds to the base peak for 2-chloro-2-methylpropane?

Accepted Answer

The base peak for 2-chloro-2-methylpropane corresponds to the m/z value of 57, which is the mass of the t-butyl cation ([C4H9]+). This is the most stable cation formed during the ionization process in mass spectrometry, making it the most abundant fragment and thus the base peak.

Question 7

Which of the following is true about the molecular weight and the M⁺•-m/z value for the following compound?

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Question 8

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 108, relative height = 61.5% (M+1)⁺•at m/z = 109, relative height = 1.5% (M+2)⁺•at m/z = 110, relative height = 61.3%

Accepted Answer

The molecular ion peak (M+) at m/z = 108 and the (M+2) peak at m/z = 110 with similar relative heights suggest the presence of bromine, which has two isotopes (79 and 81) with nearly equal abundance. C2H5Br fits this pattern.

Question 9

Which of the m/z values correspond to the molecular ion for the following compound?

Accepted Answer

The molecular ion corresponds to the peak with the highest m/z value that still contains the entire molecule, meaning it has not lost any atoms or fragments. In this case, the m/z value of 102 fits this criteria and is therefore the correct answer.

Question 10

Which of the following is true about the (M+1)⁺• peak on the mass spectrum of a hydrocarbon?

Accepted Answer

The (M+1)⁺• peak is higher than the molecular ion (M•) peak and results from the presence of one 13C isotope in the molecule. This peak is useful in calculating the number of carbon atoms in the molecule, and can also be used to distinguish between different isotopes of carbon, such as 12C and 13C. Hence, options B and D are correct.

Question 11

Compounds containing chlorine or bromine usually show a strong _____ peak.

Accepted Answer

Compounds containing chlorine or bromine show a strong M+2 peak due to the presence of isotopes ^37Cl (about 32% natural abundance) and ^81Br (about 49% natural abundance) alongside the more common ^35Cl and ^79Br, respectively. This results in a characteristic M+2 peak in mass spectra.

Question 12

Which of the following compounds will have odd m/z value for the molecular ion?

Accepted Answer

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Question 13

Which of the following mass spectra shows the presence of bromine in a compound? I  II  III  IV  Four spectra above: courtesy of SDBS: National Institute of Advanced Industrial Science and Technology

Accepted Answer

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Question 14

Which of the following mass spectra shows the presence of chlorine in a compound? I  II  III  IV  Four spectra above: courtesy of SDBS: National Institute of Advanced Industrial Science and Technology

Accepted Answer

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Question 15

Why does bromine produces M⁺• and (M+2)⁺• peaks of equal intensity on a mass spectrum?

Accepted Answer

The two isotopes of bromine that contribute to the (M+2) peak have almost equal natural abundance, which is why the peak appears with equal intensity to the M peak. Option A is incorrect because it suggests that one isotope of bromine has a higher natural abundance than the other, which is not true. Option C is also incorrect as it is the same as option A. Option D is not a valid choice as there is a correct answer.

Question 16

Which of the following will produce M⁺• and (M+2)⁺• peaks of equal intensity?

Accepted Answer

Bromine has a natural abundance of two isotopes, 79Br and 81Br. The (M+2) peak in mass spectrometry represents the presence of the heavier isotope, so if the (M+2) peak is of equal intensity to the MS peak, it indicates the presence of the heavier isotope in approximately 50% of the molecules. This can only occur in elements with multiple isotopes. Chlorine also has multiple isotopes, but nitrogen and oxygen do not have a significant enough difference in isotopic masses to produce a noticeable (M+2) peak. Therefore, the answer is C) bromine.

Question 17

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 84, relative height = 10.0% (M+1)⁺• at m/ z = 85, relative height = 0.56%

Accepted Answer

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Question 18

Provide a molecular formula that is consistent with the following mass spectral data. M⁺•at m/z = 167, relative height = 50.0% (M+1)⁺ •at m/z = 168, relative height = 4.4%

Accepted Answer

The answer of Provide a molecular formula that is consistent...

Question 19

Provide a molecular formula that is consistent with the following mass spectral data. M⁺•at m/z = 73, relative height = 86.1% (M+1)⁺•at m/z = 74, relative height = 3.2%

Accepted Answer

The answer of Provide a molecular formula that is consistent...

Question 20

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 78, relative height = 23.5% (M+1)⁺•at m/z = 79, relative height = 0.78% (M+2)⁺•at m/z = 80, relative height = 7.5%

Accepted Answer

The presence of a peak at m/z = 78 and absence of a noticeable peak at M+1 rule out options A, C, and D. The observation of a peak at M+2 rules out option E, as it predicts no peaks above M+1. Option B, C₃H₇Cl, satisfies all the observed peaks and their relative intensities.

Quiz 14: Infrared Spectroscopy and Mass Spectrometry

Which of the following will produce (M+2) ⁺ • peak one third the intensity of M⁺• peak?

Provide a molecular formula that is consistent with the following mass spectral data. M⁺•at m/z = 136, relative height = 65.6% (M+1)⁺ •at m/z = 137, relative height = 6.2%

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 72, relative height = 73.0% (M+1) ⁺•at m/z = 73, relative height = 3.3%

For which of the following compounds will the (M+2) ⁺• peak intensity be around one third the intensity of the molecular ion peak?

For which of the following compounds will the (M+2) ⁺• peak intensity be equal to the intensity of the molecular ion peak?

Which of the following m/z values corresponds to the base peak for 2-chloro-2-methylpropane?

Which of the following is true about the molecular weight and the M⁺•-m/z value for the following compound?

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 108, relative height = 61.5% (M+1) ⁺•at m/z = 109, relative height = 1.5% (M+2) ⁺•at m/z = 110, relative height = 61.3%

Which of the m/z values correspond to the molecular ion for the following compound?

Which of the following is true about the (M+1) ⁺• peak on the mass spectrum of a hydrocarbon?

Compounds containing chlorine or bromine usually show a strong _____ peak.

Which of the following compounds will have odd m/z value for the molecular ion?

Which of the following mass spectra shows the presence of bromine in a compound? I II III IV Four spectra above: courtesy of SDBS: National Institute of Advanced Industrial Science and Technology

Which of the following mass spectra shows the presence of chlorine in a compound? I II III IV Four spectra above: courtesy of SDBS: National Institute of Advanced Industrial Science and Technology

Why does bromine produces M⁺• and (M+2) ⁺• peaks of equal intensity on a mass spectrum?

Which of the following will produce M⁺• and (M+2) ⁺• peaks of equal intensity?

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 84, relative height = 10.0% (M+1) ⁺• at m/ z = 85, relative height = 0.56%

Provide a molecular formula that is consistent with the following mass spectral data. M⁺•at m/z = 167, relative height = 50.0% (M+1)⁺ •at m/z = 168, relative height = 4.4%

Provide a molecular formula that is consistent with the following mass spectral data. M⁺•at m/z = 73, relative height = 86.1% (M+1)⁺•at m/z = 74, relative height = 3.2%

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 78, relative height = 23.5% (M+1) ⁺•at m/z = 79, relative height = 0.78% (M+2) ⁺•at m/z = 80, relative height = 7.5%

Quiz 14: Infrared Spectroscopy and Mass Spectrometry

Which of the following will produce (M+2) + • peak one third the intensity of M+• peak?

Provide a molecular formula that is consistent with the following mass spectral data. M+• at m/z = 136, relative height = 65.6% (M+1)+ • at m/z = 137, relative height = 6.2%

Which molecular formula is consistent with the following mass spectral data? M+• at m/z = 72, relative height = 73.0% (M+1) +• at m/z = 73, relative height = 3.3%

For which of the following compounds will the (M+2) +• peak intensity be around one third the intensity of the molecular ion peak?

For which of the following compounds will the (M+2) +• peak intensity be equal to the intensity of the molecular ion peak?

Which of the following m/z values corresponds to the base peak for 2-chloro-2-methylpropane?

Which of the following is true about the molecular weight and the M+•-m/z value for the following compound?

Which molecular formula is consistent with the following mass spectral data? M+• at m/z = 108, relative height = 61.5% (M+1) +• at m/z = 109, relative height = 1.5% (M+2) +• at m/z = 110, relative height = 61.3%

Which of the m/z values correspond to the molecular ion for the following compound?

Which of the following is true about the (M+1) +• peak on the mass spectrum of a hydrocarbon?

Compounds containing chlorine or bromine usually show a strong _____ peak.

Which of the following compounds will have odd m/z value for the molecular ion?

Which of the following mass spectra shows the presence of bromine in a compound? I II III IV Four spectra above: courtesy of SDBS: National Institute of Advanced Industrial Science and Technology

Which of the following mass spectra shows the presence of chlorine in a compound? I II III IV Four spectra above: courtesy of SDBS: National Institute of Advanced Industrial Science and Technology

Why does bromine produces M+• and (M+2) +• peaks of equal intensity on a mass spectrum?

Which of the following will produce M+• and (M+2) +• peaks of equal intensity?

Which molecular formula is consistent with the following mass spectral data? M+• at m/z = 84, relative height = 10.0% (M+1) +• at m/ z = 85, relative height = 0.56%

Provide a molecular formula that is consistent with the following mass spectral data. M+• at m/z = 167, relative height = 50.0% (M+1)+ • at m/z = 168, relative height = 4.4%

Provide a molecular formula that is consistent with the following mass spectral data. M+• at m/z = 73, relative height = 86.1% (M+1)+• at m/z = 74, relative height = 3.2%

Which molecular formula is consistent with the following mass spectral data? M+• at m/z = 78, relative height = 23.5% (M+1) +• at m/z = 79, relative height = 0.78% (M+2) +• at m/z = 80, relative height = 7.5%

Which of the following will produce (M+2) ⁺ • peak one third the intensity of M⁺• peak?

Provide a molecular formula that is consistent with the following mass spectral data. M⁺•at m/z = 136, relative height = 65.6% (M+1)⁺ •at m/z = 137, relative height = 6.2%

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 72, relative height = 73.0% (M+1) ⁺•at m/z = 73, relative height = 3.3%

For which of the following compounds will the (M+2) ⁺• peak intensity be around one third the intensity of the molecular ion peak?

For which of the following compounds will the (M+2) ⁺• peak intensity be equal to the intensity of the molecular ion peak?

Which of the following is true about the molecular weight and the M⁺•-m/z value for the following compound?

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 108, relative height = 61.5% (M+1) ⁺•at m/z = 109, relative height = 1.5% (M+2) ⁺•at m/z = 110, relative height = 61.3%

Which of the following is true about the (M+1) ⁺• peak on the mass spectrum of a hydrocarbon?

Why does bromine produces M⁺• and (M+2) ⁺• peaks of equal intensity on a mass spectrum?

Which of the following will produce M⁺• and (M+2) ⁺• peaks of equal intensity?

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 84, relative height = 10.0% (M+1) ⁺• at m/ z = 85, relative height = 0.56%

Provide a molecular formula that is consistent with the following mass spectral data. M⁺•at m/z = 167, relative height = 50.0% (M+1)⁺ •at m/z = 168, relative height = 4.4%

Provide a molecular formula that is consistent with the following mass spectral data. M⁺•at m/z = 73, relative height = 86.1% (M+1)⁺•at m/z = 74, relative height = 3.2%

Which molecular formula is consistent with the following mass spectral data? M⁺•at m/z = 78, relative height = 23.5% (M+1) ⁺•at m/z = 79, relative height = 0.78% (M+2) ⁺•at m/z = 80, relative height = 7.5%