Mass Spectrometry
Chem 227
Name ____________________________________________
1. Alkanes
CH2
43
H3C
57
CH2
CH2
CH2
CH2
CH3
71
29
100
85
H3C
43
CH3
CH
H3C
57
CH2
CH
CH3
85
29
100
Show the fragmentation that accounts for the peaks at m/z = 43 and m/z = 57 in the mass spectrum of 2,2,3trimethylbutane. Explain why the peak at m/z = 57 is largest peak.
57
43
85
2. Isotopes
Which of the following mass spectra indicate the presence of Br, Cl, I, N, or S? The mass spectrum of an alkane is
shown for comparison. Give a brief explanation for each of your choices.
(a)
Mass spectrum of
an alkane (shown
for reference)
(b)
(c)
(d)
(e)
3. Alkenes
55
42
84
69
29
4. Aromatic Rings
91
134
Cl
112
77
114
5. Amines
NH2
30
73
6. Ethers
31
O
59
45
74
Match the following two ethers with the mass spectra described below. Give a brief but complete explanation for
your choice.
O
Spectrum #1: Major peaks at m/z = 116, 87, 73, 57, 43
butyl propyl ether
O
butyl isopropyl ether
Spectrum #2: Major peaks at m/z = 116, 101, 73, 57, 43
7. Ketones
O
43
57
71
29
100
8. Aldehydes
O
77
51
105 106
H
9. Alcohols
OH
82
100
OH
45
(M+. = 102)
69
84 87
The mass spectrum of 2,6-dimethyl-4-heptanol contains prominent peaks at m/z = 126, 111, and 87. Account for
each of these peaks.
OH
J. Ruehl 2017 Last modified by C. Orac 2025
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