N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
418
8 Mass Spectrometry
Aromatic Sulfonamides [6]
Fragmentation: In N-alkylasulfonamides, the C–C bond next to N is split preferably. In N-arylsulfonamides, besides [M - SO 2 ] +· and [M - HSO 2 ] + , the ions ar–SO 2
+
and ar'–NH + are formed.
S
O
O
N H 2
O
S
O
NH 2
O H
– SO NH
– NH 2
.
SO 2
+
C 6 H 5
+
(100% )
NH 2
C 5 H 6
+ .
– SO 2
– SO 2
– CO
– HCN
– SO 2
+ .
+ .
+ .
+ .
Ion series: Typical for the tosyl group are ions at m/z 155, 91, and 65.
Molecular ion: In arylsulfonamides, M +· is dominant. Characteristic 34 S isotope
peak at [M+2] +· and [frag+2] for S-containing fragments (4.5% per S atom).
8.10.5 Thiocarboxylic Acid S-Esters [7]
Fragmentation: In contrast to esters, the major fragmentation process is elimination
of the alkyl radical from the thiol site. Ethylene sulfide is eliminated from thioesters
with longer alkyl chains. Aromatic dithiocarboxylic acid esters usually fragment in
two steps to the aryl cation.
O
R
S
alk
– alk
.
O
R
S
+
O
S
R
R
S
–
R
O
R
+
[M –60]
+ .
SR
S
C S
+
C 6 H 5
+
– CS
– SR
.
m/z 121
+ .
+ .
+ .
.