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NUCLEAR MAGNETIC RESONANCE AND MASS SPECTROMETRY 165
C is 1-bromopentane. The following are the signal assignments.
(e) (c) (a)
(d ) (b)
Br
(a) δ 14
(b) δ 23
(c) δ 30
(d) δ 33
(e) δ 34
9.17 A peak at M .+−15 involves the loss of a methyl radical and the formation of a 1◦ or 2◦
carbocation.
CH3
+
+
(M+−15)(M+)
+
or
CH3+
(M+−15)
+
+
(M+)
A peak at M .+−29 arises from the loss of an ethyl radical and the formation of a 2◦ carbo-
cation.
+
(M+−29)
+
+
(M+)
Since a secondary carbocation is more stable than a methyl carbocation, and since there
are two cleavages that form secondary carbocations by loss of an ethyl radical, the peak at
M .+−29 is more intense.
9.18 After loss of a pi bonding electron through electron impact ionization, both peaks arise
from allylic fragmentations:
+
Allyl radical m/z 57
m/z 41 
Allyl cation
+
+
++ +
9.19 The spectrum given in Fig. 9.40 is that of butyl isopropyl ether. The main clues are the
peaks at m/z 101 and m/z 73 due to the following fragmentations.