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CHM 332 > Chapter 14 > Flashcards

Chapter 14 Flashcards

1
Q

What is the principle that allows us to use mass spectrometry to determine the molecular weight of a compound?
A. higher molecular weight compounds are less volatile
B. higher molecular weight compounds are more dense
C. a beam of higher molecular weight cations is deflected less by a magnetic field
D. ions with higher molecular weight absorb higher frequencies of light

A

C. a beam of higher molecular weight cations is deflected less by a magnetic field

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2
Q

What is the x-axis of a mass spectrum?
A. mass
B. mass/energy
C. mass/charge
D. charge

A

C. mass/charge

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3
Q
  1. What is the y-axis of a mass spectrum?
    A. mass
    B. energy
    C. abundance
    D. field strength
A

C. abundance

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4
Q
  1. Which of the following is the definition of the base peak of a mass spectrum?
    A. the peak corresponding to the most abundant ion
    B. the peak corresponding to the ion with lowest m/e
    C. the peak corresponding to the molecular ion peak
    D. the peak corresponding to the ion arising to loss of a proton from the molecular ion
A

A. the peak corresponding to the most abundant ion

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5
Q
  1. Which of the following corresponds to the molecular ion in EI mass spectrometry?
    A. the most abundant ion
    B. the ion with the smallest m/e
    C. the ion formed by removal of an electron from the molecule
    D. any ion formed by fragmentation of the molecule
A

C. the ion formed by removal of an electron from the molecule

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6
Q
  1. Which of the following sets of molecular ions does an alkyl bromide possess?
    A. two molecular ions in a 2:1 ratio separated by two mass units
    B. two molecular ions in a 1:1 ratio separated by two mass units
    C. three molecular ions in a 1:2:1 ratio separated by two mass units
    D. two molecular ions in a 3:1 ratio separated by two mass units
A

B. two molecular ions in a 1:1 ratio separated by two mass units

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7
Q
  1. Which of the following sets of molecular ions does an alkyl chloride possess?
    A. two molecular ions in a 2:1 ratio separated by two mass units
    B. two molecular ions in a 1:1 ratio separated by two mass units
    C. three molecular ions in a 1:2:1 ratio separated by two mass units
    D. two molecular ions in a 3:1 ratio separated by two mass units
A

D. two molecular ions in a 3:1 ratio separated by two mass units

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8
Q
  1. Which of the following sets of molecular ions does a dibromoalkane possess?
    A. two molecular ions in a 2:1 ratio separated by two mass units
    B. two molecular ions in a 1:1 ratio separated by two mass units
    C. three molecular ions in a 1:2:1 ratio, separated by two mass units
    D. two molecular ions in a 3:1 ratio separated by two mass units
A

C. three molecular ions in a 1:2:1 ratio, separated by two mass units

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9
Q
  1. Which of the following is most consistent with a molecule having a molecular ion with m/e of 77?
    A. the molecule contains bromine
    B. the molecule contains nitrogen
    C. the molecule is an alcohol
    D. the molecule is a hydrocarbon
A

B. the molecule contains nitrogen

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10
Q
  1. How many carbon atoms are present in a molecule which gives an M+1 peak that is 5.74% of the intensity of the molecular ion?
    A. 5
    B. 6
    C. 11
    D. 12
A

A. 5

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11
Q
  1. How many carbon atoms are present in a molecule which gives an M+1 peak that is 11.48% of the intensity of the molecular ion?
    A. 5
    B. 6
    C. 11
    D. 12
A

C. 11

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12
Q
  1. What are the most common products of the fragmentation of a molecular ion?
    A. two radicals
    B. an anion and a cation
    C. a radical and a cation
    D. two cations
A

C. a radical and a cation

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13
Q
A

A. i

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14
Q
  1. Which of the following gives rise to a prominent M - 18 peak in the mass spectrum?
    A. hexane
    B. 1-chloropentane
    C. 1-pentanol
    D. 3-methylpentane
A

C. 1-pentanol

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15
Q
  1. Which of the following gives rise to a prominent M - 15 peak in the mass spectrum?
    A. hexane
    B. 1-chloropentane
    C. 1-pentanol
    D. 3-methylpentane
A

D. 3-methylpentane

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16
Q
  1. Which of the following gives rise to a prominent M - 15 peak in the mass spectrum?
    A. cyclopentane
    B. cyclopentene
    C. cyclopentanol
    D. methylcyclopentane
A

D. methylcyclopentane

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17
Q

1) Which of the following molecular changes is necessary for mass spectrometry to occur?

A) excitation of an electron from the ground state to higher energy state

B) change of alignment of an electron in a magnetic field

C) change of alignment of a proton in a magnetic field

D) loss of an electron

E) molecular vibration

A

D) loss of an electron

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18
Q

2) Which of the following statements is true about a molecular ion?

A) It is a compound that lost a pair of electrons.

B) It is a compound that gained a pair of electrons.

C) It is a compound that gained one electron.

D) It is a compound that lost one electron.

E) It is a compound that carries a free radical and a negative charge.

A

D) It is a compound that lost one electron.

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19
Q

3) Which of the following statements best describes the meaning of the following species:

[CH3CH2CH3] ∙ + ?

A) It is the molecular ion of propane.

B) It is the parent ion of propane.

C) It is the radical cation of propane.

D) The m/z value is 44.

E) all of the above

A

E) all of the above

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20
Q

4) Which of the following m/z values is the molecular ion for 2-butanone?

A

E) 72

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21
Q

7) Which of the following statements best explains the information we can gain from mass spectrometry?

A) It allows us to determine the number of protons in a compound.

B) It allows us to determine the kinds of functional groups in a compound.

C) It allows us to determine the molecular weight and the mass of some fragments of a compound.

D) It allows us to determine the presence and nature of a carbocation in the compound.

E) It allows us to determine the presence and nature of a free radical in the compound.

A

C) It allows us to determine the molecular weight and the mass of some fragments of a compound.

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22
Q

8) Which of the following is true about the base peak in mass spectrometry?

A) The m/z value equals the molecular weight of the compound.

B) The m/z value corresponds to a very stable carbanion.

C) It has the largest peak height in the spectrum.

D) It has the highest m/z value of all the peaks in the spectrum.

E) The base peak is assigned a relative abundance equal to that of the parent ion.

A

C) It has the largest peak height in the spectrum.

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23
Q

9) What m/z value would you predict for the most stable fragment peak in the mass spectrum of 4-ethylheptane?

A) 128

B) 127

C) 113

D) 99

E) 85

A

B) 127

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24
Q

12) Which of the following is not a major peak in the MS of isopentane?

A) 29

B) 43

C) 57

D) 60

E) 72

A

D) 60

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25
Q

14) Give the m/z ratio that corresponds to the molecular ion in the mass spectrum of 2-pentanone.

A) 28

B) 43

C) 58

D) 71

E) 86

A

E) 86

26
Q

17) Which of the following is not true about the M+1 peak?

A) It is one m/z unit higher than the base peak.

B) It is one m/z unit higher than the molecular ion peak.

C) It is one m/z unit higher than the parent ion peak.

D) It occurs because there is more than one naturally occurring isotope of carbon.

E) This means that the number of carbon atoms in a compound can be calculated if the relative abundance of both the M and M+1 peaks is known.

A

A) It is one m/z unit higher than the base peak.

27
Q

18) Which of the following statements best explains how a hydrocarbon can show an M+2 peak in mass spectrometry?

A) from 13C and 1H

B) from 12C and 2H

C) from a single 13C

D) from a single 3H

E) from two 13C’s

A

E) from two 13C’s

28
Q

19) Predict the molecular formula of the compound represented below based on the MS data given.

A

E) C5H8O

29
Q

20) Which of the following characterizes the unusually intense peak of alkyl chlorides in MS spectrometry?

A) M + 1 peak

B) M + 2 peak

C) base peak

D) parent peak

E) none of the above

A

B) M + 2 peak

30
Q

21) Which compound’s mass spectrum shows peaks at M, M+2, and M+4 whose abundances are in a ratio of 1:2:1?

A) cyclohexanol

B) chlorocyclohexane

C) 1,2-dichlorocyclohexane

D) 1-bromopentane

E) 1,5-dibromopentane

A

E) 1,5-dibromopentane

31
Q

27) In the mass spectrum of 2-chloropropane, what is the m/z of the molecular ion peak of greatest intensity?

A) 63

B) 76

C) 78

D) 80

E) 82

A

C) 78

32
Q

28) In the mass spectrum of 1,2-dichloroethane, what is the m/z of the molecular ion peak of greatest intensity?

A) 94

B) 96

C) 98

D) 100

E) 102

A

C) 98

33
Q

29) In the mass spectrum of bromoform, CHBr3, molecular ion peaks appear at m/z 250, 251, 252, and 253? What is the ratio of the intensities of these peaks?

A) 1:1:1:1

B) 1:2:2:1

C) 1:3:3:1

D) 2:3:3:2

E) 3:2:2:3

A

C) 1:3:3:1

34
Q

32) Which of the following is the base peak for the compound below?

A

D) 57

35
Q

33) Which of the following structures will give a base peak of 43 in mass spectrometry?

A

C

36
Q

35) Which of the following m/z values is least intense in the mass spectrum of 1-chloropropane?

A) 80

B) 79

C) 78

D) 65

E) 63

A

B) 79

37
Q

36) Which of the following is/are true about the MS of 1-bromobutane?

A) Peaks of approximately equal intensity are observed at m/z 136 and 138.

B) The major fragmentation occurs by cleavage of the C-Br bond.

C) The most intense peak occurs at m/z 43.

D) both A and B

E) both B and C

A

D) both A and B

38
Q
  1. Which of the molecules gives rise to a molecular ion with an odd value of m/e?
    A. C6H12Cl2
    B. C7H10N2
    C. C8H13N
    D. C8H14Br2
A

C. C8H13N

39
Q
  1. Which of the molecules gives rise to a molecular ion with an odd value of m/e?
    A. C6H12O2
    B. C7H10ClN
    C. C8H18N2
    D. C8H12
A

B. C7H10ClN

40
Q
  1. Which of the following is not prominent in the mass spectrum of 2-methyl-2-butanol?
    A. M - 29
    B. M - 18
    C. M - 15
    D. M - 12
A

D. M - 12

41
Q
  1. Which of the following gives rise to a prominent peak in the mass spectrum at m/z of 39?
    A. 1-octyne
    B. 4-octyne
    C. 5-methyl-3-octyne
    D. 2,2-dimethyl-3-heptyne
A

A. 1-octyne

42
Q
  1. Which of the following does not give rise to a prominent M - 41 peak in the mass spectrum?
    A. 1-hexene
    B. 3-methyl-1-hexene
    C. 4-methyl-1-hexene
    D. 5-methyl-1-hexene
A

B. 3-methyl-1-hexene

43
Q
  1. Which of the following is not prominent in the mass spectrum of 2-methyl-2-butanol?
    A. M - 15
    B. M - 18
    C. M - 21
    D. M - 29
A

B. M - 18

44
Q
  1. Which of the following alcohols does not give a prominent M - 15 ion?
    A. isopropyl alcohol
    B. tert-butyl alcohol
    C. 2-hexanol
    D. 3-pentanol
A

D. 3-pentanol

45
Q
  1. Which of the following gives rise to a prominent M - 18 peak in the mass spectrum?
    A. cyclohexane
    B. cyclohexene
    C. 1-chlorocyclohexane
    D. cyclohexanol
A

D. cyclohexanol

46
Q
  1. Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 41?
    A. 1-hexene
    B. 2-hexyne
    C. 3-hexanol
    D. 2-chlorohexane
A

A. 1-hexene

47
Q
  1. Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 43?
    A. 1-hexanol
    B. 2-hexanol
    C. hexanal
    D. hexanoic acid
A

C. hexanal

48
Q
  1. Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 45?
    A. 1-hexanol
    B. 2-hexanol
    C. hexanal
    D. hexanoic acid
A

D. hexanoic acid

49
Q
  1. Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 60?
    A. 1-hexanol
    B. 2-hexanol
    C. hexanal
    D. hexanoic acid
A

D. hexanoic acid

50
Q
  1. Which of the following gives rise to a prominent peak in the mass spectrum with m/z of M - 31?
    A. 2-methylhexanoic acid
    B. methyl hexanoate
    C. ethyl hexanoate
    D. hexanoic acid
A

B. methyl hexanoate

51
Q
  1. Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 91?
    A. 1-octene
    B. 1-hexanamine, CH3CH2CH2CH2CH2CH2NH2
    C. benzene
    D. ethylbenzene
A

D. ethylbenzene

52
Q
  1. Which of the following gives rise to a prominent peak in the mass spectrum with m/z of 30?
    A. 1-hexanamine, CH3CH2CH2CH2CH2CH2NH2
    B. 1,1-dimethyl-1-butanamine, CH3CH2CH2C(CH3)2NH2
    C. 1-hexanol
    D. hexanal
A

A. 1-hexanamine, CH3CH2CH2CH2CH2CH2NH2

53
Q

30) Which of the following m/z values is the base peak for benzyl alcohol?

A

C

54
Q

31) Which of the following compounds exhibits the pattern of m/z values shown below?

41, 43, 57, 87, 101, 116

A) propylbromide

B) isopropyl bromide

C) sec-butyl isopropyl ether

D) 2-hexanol

E) 2-butanone

A

C) sec-butyl isopropyl ether

55
Q

34) The mass spectra of alcohols often fail to exhibit detectable M peaks but instead show relatively large ________ peaks.

A) M+1

B) M+2

C) M-16

D) M-17

E) M-18

A

E) M-18

56
Q

37) An acylium ion is often produced as a fragment in the MS of which of the following class of organic compounds?

A) ketones

B) ethers

C) alkyl halides

D) alcohols

E) peroxides

A

A) ketones

57
Q

41) Give the ion that corresponds a m/z ratio of 31 in a mass spectrum of 1-butanol.

A

B

58
Q

42) Give the ion that corresponds to a m/z ratio of 56 in a mass spectrum of 1-butanol.

A

C

59
Q

43) Give the ion that corresponds to a m/z ratio of 58 in a mass spectrum of 2-pentanone.

A

A

60
Q

46) Ethyl acetate has the structure CH3CO2CH2CH3. Which set of m/z peaks is most consistent with this structure?

A) 88, 73, 43

B) 88, 76, 45

C) 88, 73, 45

D) 88, 76, 43

E) 88, 72, 70, 44

A

A) 88, 73, 43

61
Q

47) Which m/z peak is expected to be the base peak of cyclopentanol?

A) 57

B) 43

C) 29

D) 85

E) 86

A

A) 57

62
Q

48) When cyclopentanol is treated with chromic acid, the alcohol is oxidized to cyclopentanone. Which m/z peak is expected to be the base peak of cyclopentanone?

A) 55

B) 43

C) 29

D) 84

E) 85

A

A) 55

CHM 332 (12 decks)

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