N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
8.10 Sulfur Compounds
417
8.10.4 Sulfonic Acids and Their Esters and Amides
Aromatic Sulfonic Acids [6]
Fragmentation: The most prominent fragment, [M - HSO 3 ] + (Δm 81), is formed in
a two-step process. In the first step, OH · elimination leads to a weak fragment ion
[M - OH] + (Δm 17). If an alkyl group is present in ortho position, [M - H 2 SO 3 ] +·
(Δm 82) is formed instead of [M-81] + . Other important fragments are [M - SO 2 ] +·
(Δm 64), [M - HSO 2 ] + (Δm 65), and [M - SO 3 ] +· (Δm 80).
Ion series: Aromatic hydrocarbon fragments, C n H n and C n H n±1 (m/z 39, 51–53,
63–65, 75–77, ...), and O-containing aromatic fragments at higher masses.
Intensities: Intensive peaks mainly in the higher mass range.
Molecular ion: Very strong. Characteristic 34 S isotope peak at [M+2] +· and [frag+2]
for S-containing fragments (4.5% per S atom).
Alkylsulfonic Acid Esters [6]
Fragmentation: Loss of alkyl by fragmentation of the C–O bond with concomitant
double H rearrangement to form the protonated sulfonic acid ion (m/z 97
for methanesulfonates), which then loses water. Loss of the alkoxyl residue
(fragmentation of the S–O bond). Formation of an alkene ion from the alkyl ester
group by a McLafferty-type rearrangement. In aryl esters, the phenoxy ion and the
phenol radical cations dominate the spectrum.
Ion series: Besides RSO 3 H 2
+ and RSO 2
+ (m/z 97 and 79 for methanesulfonates),
for aliphatic esters mainly alkene fragments. In aryl esters, aromatic fragments,
C n H n and C n H n±1 (m/z 39, 51–53, 63–65, 75–77, …), as well as O-containing
aromatic fragments at higher masses.
Intensities: Intensive peaks in the lower mass range.
Molecular ion: Small or negligible signal for alkyl esters; intensive for aryl esters.
Characteristic 34 S isotope peak at [M+2] +· and [frag+2] for S-containing fragments
(4.5% per S atom).
Arylsulfonic Acid Esters [6]
Fragmentation: Dominating fragments resulting from cleavage of the S–O
bond (leading to the ar–SO 2
+ ion), which loses SO 2 (m/z 155 and 91 for
p-toluenesulfonates). In arylsulfonates with longer chains, double H rearrangement
to give the protonated acid (m/z 173 for p-toluenesulfonates).
Ion series: Aromatic hydrocarbon fragments, C n H n and C n H n±1 (m/z 39, 51–53,
63–65, 75–77, …).
Intensities: Intensive peaks mainly in the higher mass range.
Molecular ion: Medium or weak. Characteristic 34 S isotope peak at [M+2] +· and
[frag+2] for S-containing fragments (4.5% per S atom).
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
8.10 Sulfur Compounds
417
8.10.4 Sulfonic Acids and Their Esters and Amides
Aromatic Sulfonic Acids [6]
Fragmentation: The most prominent fragment, [M - HSO 3 ] + (Δm 81), is formed in
a two-step process. In the first step, OH · elimination leads to a weak fragment ion
[M - OH] + (Δm 17). If an alkyl group is present in ortho position, [M - H 2 SO 3 ] +·
(Δm 82) is formed instead of [M-81] + . Other important fragments are [M - SO 2 ] +·
(Δm 64), [M - HSO 2 ] + (Δm 65), and [M - SO 3 ] +· (Δm 80).
Ion series: Aromatic hydrocarbon fragments, C n H n and C n H n±1 (m/z 39, 51–53,
63–65, 75–77, ...), and O-containing aromatic fragments at higher masses.
Intensities: Intensive peaks mainly in the higher mass range.
Molecular ion: Very strong. Characteristic 34 S isotope peak at [M+2] +· and [frag+2]
for S-containing fragments (4.5% per S atom).
Alkylsulfonic Acid Esters [6]
Fragmentation: Loss of alkyl by fragmentation of the C–O bond with concomitant
double H rearrangement to form the protonated sulfonic acid ion (m/z 97
for methanesulfonates), which then loses water. Loss of the alkoxyl residue
(fragmentation of the S–O bond). Formation of an alkene ion from the alkyl ester
group by a McLafferty-type rearrangement. In aryl esters, the phenoxy ion and the
phenol radical cations dominate the spectrum.
Ion series: Besides RSO 3 H 2
+ and RSO 2
+ (m/z 97 and 79 for methanesulfonates),
for aliphatic esters mainly alkene fragments. In aryl esters, aromatic fragments,
C n H n and C n H n±1 (m/z 39, 51–53, 63–65, 75–77, …), as well as O-containing
aromatic fragments at higher masses.
Intensities: Intensive peaks in the lower mass range.
Molecular ion: Small or negligible signal for alkyl esters; intensive for aryl esters.
Characteristic 34 S isotope peak at [M+2] +· and [frag+2] for S-containing fragments
(4.5% per S atom).
Arylsulfonic Acid Esters [6]
Fragmentation: Dominating fragments resulting from cleavage of the S–O
bond (leading to the ar–SO 2
+ ion), which loses SO 2 (m/z 155 and 91 for
p-toluenesulfonates). In arylsulfonates with longer chains, double H rearrangement
to give the protonated acid (m/z 173 for p-toluenesulfonates).
Ion series: Aromatic hydrocarbon fragments, C n H n and C n H n±1 (m/z 39, 51–53,
63–65, 75–77, …).
Intensities: Intensive peaks mainly in the higher mass range.
Molecular ion: Medium or weak. Characteristic 34 S isotope peak at [M+2] +· and
[frag+2] for S-containing fragments (4.5% per S atom).