Question 1

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of M - 31?

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Question 2

What is the most likely molecular formula of a compound that has a molecular ion in the EI mass spectrum with m/z of 97 and an M+1 peak that is 6.6% of the intensity of the molecular ion peak?

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Question 3

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 91?

Accepted Answer

Ethylbenzene has a molecular formula of C8H10, which gives a fragment ion of m/z 91 in the mass spectrum due to the loss of a methyl group. None of the other options have a molecular formula that gives rise to a fragment ion at m/z 91.

Question 4

Which of the following does not give rise to a prominent M - 41 peak in the mass spectrum?

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Question 5

What is the most likely molecular formula of a compound that has a molecular ion in the EI mass spectrum with m/z of 136, with a M+1 and M+2 peaks that are 4.4% and 49% of the intensity of the molecular ion peak, respectively.

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Question 6

What is the most likely moleuclar formula of a compound (that contains only C, H and O) which has a molecular ion in the EI mass spectrum with m/z of 104 and an M+1 peak that is 5.5% of the intensity of the molecular ion peak?

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Question 7

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 30?

Accepted Answer

The prominent peak at m/z 30 in a mass spectrum typically corresponds to the methyl cation (CH3+), which can be formed by the fragmentation of a molecule that contains a methyl group. Of the given choices, only 1-hexanamine contains a methyl group, specifically on the sixth carbon atom, which can easily lose a hydrogen to form the methyl cation during ionization and fragmentation.

Question 8

What is the most likely moleuclar formula of a compound that has a molecular ion in the EI mass spectrum with m/z of 120, with a M+1 and M+2 peaks that are 6.6% and 24% of the intensity of the molecular ion peak, respectively.

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Question 9

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 43?

Accepted Answer

Hexanal tends to form a prominent fragment with a m/z of 43 due to the cleavage of the aldehyde group, leading to a stable aldehyde cation fragment.

Question 10

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 41?

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Question 11

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 45?

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Question 12

Which of the following gives rise to a prominent M - 15 peak in the mass spectrum?

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Question 13

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 60?

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Question 14

Which of the following gives rise to a prominent M - 18 peak in the mass spectrum?

Accepted Answer

1-pentanol gives rise to a prominent M - 18 peak in the mass spectrum due to the loss of a water molecule (H2O, 18 Da) from the alcohol group during ionization.

Question 15

Which of the following gives rise to a prominent M - 18 peak in the mass spectrum?

Accepted Answer

Cyclohexanol can lose a water molecule (H2O, 18 Da) during mass spectrometry, leading to a prominent M-18 peak.

Question 16

Which of the following gives rise to a prominent M - 15 peak in the mass spectrum?

Accepted Answer

The presence of a methyl group in a cyclic structure can lead to a prominent M-15 peak in the mass spectrum, which corresponds to the loss of a methyl radical (CH3) from the parent molecule. Therefore, the correct choice is methylcyclopentane (D) which contains a methyl group attached to the cyclopentane ring. The other choices do not contain a methyl group and would not show a prominent M-15 peak.

Question 17

Which of the following gives rise to a prominent peak in the mass spectrum at m/z of 39?

Accepted Answer

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Question 18

Which of the following alcohols does not give a prominent M - 15 ion?

Accepted Answer

The M-15 ion comes from the loss of a methyl group from the molecular ion (M) of an alcohol. Isopropyl alcohol (A) and tert-butyl alcohol (B) both have prominent M-15 ions because they both have methyl groups attached to the tertiary carbon. 2-hexanol (C) also has a prominent M-15 ion because it has a methyl group attached to the secondary carbon. However, 3-pentanol (D) does not have a prominent M-15 ion because it does not have a methyl group attached to the primary carbon.

Question 19

Which of the following is not prominent in the mass spectrum of 2-methyl-2-butanol?

Accepted Answer

In the mass spectrum of 2-methyl-2-butanol, the peak for M - 18 is not prominent because it corresponds to the loss of a water molecule (H2O), which is less common for alcohols when compared to the loss of smaller fragments such as methyl (M - 15) or ethyl groups (M - 29), or specific rearrangements leading to other fragment losses.

Quiz 14: Mass Spectrometry

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of M - 31?

What is the most likely molecular formula of a compound that has a molecular ion in the EI mass spectrum with m/z of 97 and an M+1 peak that is 6.6% of the intensity of the molecular ion peak?

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 91?

Which of the following does not give rise to a prominent M - 41 peak in the mass spectrum?

What is the most likely molecular formula of a compound that has a molecular ion in the EI mass spectrum with m/z of 136, with a M+1 and M+2 peaks that are 4.4% and 49% of the intensity of the molecular ion peak, respectively.

What is the most likely moleuclar formula of a compound (that contains only C, H and O) which has a molecular ion in the EI mass spectrum with m/z of 104 and an M+1 peak that is 5.5% of the intensity of the molecular ion peak?

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 30?

What is the most likely moleuclar formula of a compound that has a molecular ion in the EI mass spectrum with m/z of 120, with a M+1 and M+2 peaks that are 6.6% and 24% of the intensity of the molecular ion peak, respectively.

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 43?

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 41?

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 45?

Which of the following gives rise to a prominent M - 15 peak in the mass spectrum?

Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 60?

Which of the following gives rise to a prominent M - 18 peak in the mass spectrum?

Which of the following gives rise to a prominent M - 18 peak in the mass spectrum?

Which of the following gives rise to a prominent M - 15 peak in the mass spectrum?

Which of the following gives rise to a prominent peak in the mass spectrum at m/z of 39?

Which of the following alcohols does not give a prominent M - 15 ion?

Which of the following is not prominent in the mass spectrum of 2-methyl-2-butanol?