N
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
398
8 Mass Spectrometry
Occasionally, an alkane is eliminated after cleavage of the C–C bond adjacent to
the O atom:
[ArOCH 2 R + H] +
ArOCH 2
+ + RH
Ion series: Mostly aromatic fragments, C n H n and C n H n±1 (m/z 39, 51–53, 63–65,
75–77, …).
Intensities: Usually maximum at the mass of the corresponding phenol. Otherwise,
intensive peaks mainly concentrated in the high and medium mass range.
Molecular ion: Strong.
Aromatic Ethers
Fragmentation: Loss of H · (Δm 1), CO (Δm 28), and CHO · (Δm 29) from M +· .
Cleavage at the C–O bond and decarbonylation of the resulting product, followed
by dehydrogenation.
ESI-MS/MS: In diaryl ethers, homolytic cleavage of an Aryl–O bond leads to an
aromatic radical cation:
[Ar 1 OAr 2 + H] +
Ar 1 O
.
+ [Ar 2 H] + .
Ion series: Aromatic fragments corresponding to 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 M +· region.
Molecular ion: Strong.
8.8.4 Aliphatic Epoxides [9]
Fragmentation: The most important primary fragmentation is the cleavage of C–C
bonds next to the O atom (α-cleavage), resulting in complex degradation due to
the related multiple choice and extensive secondary rearrangements. The products
allow mass-spectrometric localization of double bonds after epoxidation.
Due to ring opening prior to fragmentation, β-cleavage is as relevant as the
α-cleavage.
O
R
R
O
O
+
+
– CH 2 R
m/z 57
+ .
.
.
γ-Cleavage is the most important fragmentation mechanism, especially in terminal
epoxides:
O
R
R
O
O
+
+
– R
.
m/z 71
+ .
.
X
C
O
N
S
Hal
Solvents
Natural
Products
P Si
C
C
C C
C
C
398
8 Mass Spectrometry
Occasionally, an alkane is eliminated after cleavage of the C–C bond adjacent to
the O atom:
[ArOCH 2 R + H] +
ArOCH 2
+ + RH
Ion series: Mostly aromatic fragments, C n H n and C n H n±1 (m/z 39, 51–53, 63–65,
75–77, …).
Intensities: Usually maximum at the mass of the corresponding phenol. Otherwise,
intensive peaks mainly concentrated in the high and medium mass range.
Molecular ion: Strong.
Aromatic Ethers
Fragmentation: Loss of H · (Δm 1), CO (Δm 28), and CHO · (Δm 29) from M +· .
Cleavage at the C–O bond and decarbonylation of the resulting product, followed
by dehydrogenation.
ESI-MS/MS: In diaryl ethers, homolytic cleavage of an Aryl–O bond leads to an
aromatic radical cation:
[Ar 1 OAr 2 + H] +
Ar 1 O
.
+ [Ar 2 H] + .
Ion series: Aromatic fragments corresponding to 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 M +· region.
Molecular ion: Strong.
8.8.4 Aliphatic Epoxides [9]
Fragmentation: The most important primary fragmentation is the cleavage of C–C
bonds next to the O atom (α-cleavage), resulting in complex degradation due to
the related multiple choice and extensive secondary rearrangements. The products
allow mass-spectrometric localization of double bonds after epoxidation.
Due to ring opening prior to fragmentation, β-cleavage is as relevant as the
α-cleavage.
O
R
R
O
O
+
+
– CH 2 R
m/z 57
+ .
.
.
γ-Cleavage is the most important fragmentation mechanism, especially in terminal
epoxides:
O
R
R
O
O
+
+
– R
.
m/z 71
+ .
.