N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
8.10 Sulfur Compounds
411
8.10 Sulfur Compounds [1]
8.10.1 Thiols
Aliphatic Thiols [2]
Fragmentation: Elimination of H 2 S (Δm 34; or SH, Δm 33, from secondary thiols)
followed by loss of alkenes; consecutive losses of ethylene from unbranched thiols.
Cleavage of the α,β-C–C bond (next to the SH group) leads to CH 2 SH + (m/z 47).
Note that this fragment also occurs in secondary and tertiary thiols. The S atom is
poorer than N, but better than O, at stabilizing such a fragment. Cleavage at the next
C–C bonds leads to signals at m/z 61, 75, and 89. In secondary and tertiary thiols,
prominent fragments are formed by loss of the largest α-alkyl group.
Ion series: Dominant alkenyl fragments (C n H 2n-1 , m/z 41, 55, 69, …) and smaller
aliphatic fragments (C n H 2n+1 , m/z 43, 57, 71, …). Sulfur-containing aliphatic
fragments: C n H 2n+1 S (m/z 47, 61, 75, 89, …). Often significant sulfur-indicating
fragments: HS + , H 2 S +· , H 3 S + , and CHS + (m/z 33, 34, 35, and 45).
Intensities: More intensive peaks in the lower mass range, mostly of the alkene
type. Characteristic local maxima from S-containing fragments, C n H 2n+1 S (m/z 47,
61, 75, 89, …). In n-alkyl thiols, the intensity of the signal at m/z 61 is roughly half
that of m/z 47; the signal at m/z 89 is more intensive than that at m/z 75, presumably
because it is stabilized by cyclization.
Molecular ion: Relatively strong except for higher tertiary thiols. Characteristic 34 S
isotope peak at [M+2] +· and [frag+2] for S-containing fragments (4.5% per S atom).
Aromatic Thiols [2]
Fragmentation: CS elimination from M +· and [M-1] + , yielding [M-44] +· and
[M-45] + . HS· elimination from M +· to give [M-33] + .
Ion series: HCS + (m/z 45) is characteristic besides the aromatic fragments, C n H n
and C n H n±1 (m/z 39, 51–53, 63–65, 75–77, …).
Intensities: Intensive peaks in the higher mass range.
Molecular ion: Usually dominating; base peak in thiophenol. [M-1] + is usually
strong. 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
411
8.10 Sulfur Compounds [1]
8.10.1 Thiols
Aliphatic Thiols [2]
Fragmentation: Elimination of H 2 S (Δm 34; or SH, Δm 33, from secondary thiols)
followed by loss of alkenes; consecutive losses of ethylene from unbranched thiols.
Cleavage of the α,β-C–C bond (next to the SH group) leads to CH 2 SH + (m/z 47).
Note that this fragment also occurs in secondary and tertiary thiols. The S atom is
poorer than N, but better than O, at stabilizing such a fragment. Cleavage at the next
C–C bonds leads to signals at m/z 61, 75, and 89. In secondary and tertiary thiols,
prominent fragments are formed by loss of the largest α-alkyl group.
Ion series: Dominant alkenyl fragments (C n H 2n-1 , m/z 41, 55, 69, …) and smaller
aliphatic fragments (C n H 2n+1 , m/z 43, 57, 71, …). Sulfur-containing aliphatic
fragments: C n H 2n+1 S (m/z 47, 61, 75, 89, …). Often significant sulfur-indicating
fragments: HS + , H 2 S +· , H 3 S + , and CHS + (m/z 33, 34, 35, and 45).
Intensities: More intensive peaks in the lower mass range, mostly of the alkene
type. Characteristic local maxima from S-containing fragments, C n H 2n+1 S (m/z 47,
61, 75, 89, …). In n-alkyl thiols, the intensity of the signal at m/z 61 is roughly half
that of m/z 47; the signal at m/z 89 is more intensive than that at m/z 75, presumably
because it is stabilized by cyclization.
Molecular ion: Relatively strong except for higher tertiary thiols. Characteristic 34 S
isotope peak at [M+2] +· and [frag+2] for S-containing fragments (4.5% per S atom).
Aromatic Thiols [2]
Fragmentation: CS elimination from M +· and [M-1] + , yielding [M-44] +· and
[M-45] + . HS· elimination from M +· to give [M-33] + .
Ion series: HCS + (m/z 45) is characteristic besides the aromatic fragments, C n H n
and C n H n±1 (m/z 39, 51–53, 63–65, 75–77, …).
Intensities: Intensive peaks in the higher mass range.
Molecular ion: Usually dominating; base peak in thiophenol. [M-1] + is usually
strong. Characteristic 34 S isotope peak at [M+2] +· and [frag+2] for S-containing
fragments (4.5% per S atom).