N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
8.7 Halogen Compounds
391
Polyhaloalkanes
Fragmentation: Preferred fragmentation of the C–C bond if several halogen atoms
are bonded to one of these carbon atoms. CF 3 (m/z 69) is often the base peak in
terminally perfluorated alkanes, and so is CHCl 2 (m/z 83, 85, 87) in terminally
dichlorinated compounds. Often, X 2 is eliminated besides the usual fragmentation
of X · and HX. Interchange of halogens may occur. For example, m/z 85 (CF 2 Cl) is
a dominant signal (≈ 60%) for CF 3 CFCl 2 .
Ion series: Most fragments are halogenated alkyl and alkenyl groups, easily
detectable on the basis of the isotope signals in the cases of Cl and Br.
Intensities: Intensive peaks mainly in the lower mass range.
Molecular ion: Weak, decreasing with increasing number of halogen atoms. Absent
from the spectra of many polyhalogenated compounds.
Aromatic Halides
Fragmentation: Consecutive losses of halogen radicals and/or acid HX. In
perhalogenated aromatics, decomposition down to C x
+ , with x from 1 to 6 (m/z 12,
24, 36, 48, 60, 72). If alkyl-substituted (C n > 1 ), the base peak is mostly the result of
benzylic cleavage. In an otherwise aromatic environment, m/z 57 is a F indicator
(C 3 H 2 F + ). Elimination of CF 2 (Δm 50) from CF 3 groups attached to the aromatic
ring (from M +· or fragments).
Ion series: Aromatic fragments, C n H n , C n H n-1 , and C n H n-2 (m/z 39, 51–53, 63–65,
75–77, …). In the higher mass range: C n (H,X) n .
Intensities: Dominant peaks in the M +· region.
Molecular ion: Usually very strong. Characteristic isotope signals for Cl and Br.
References
[1] A.G. Loudon, Mass spectrometry and the carbon-halogen bond. In: The
Chemistry of the Carbon-Halogen Bond, Part 1; S. Patai, Ed.; Wiley: London,
1973; p 223.
[2] D.G.I. Kingston, B.W. Hobrock, M.M. Bursey, J.T. Bursey, Intramolecular
hydrogen transfer in mass spectra. III. Rearrangements involving the loss of
small neutral molecules, Chem. Rev. 1975, 75, 693.
[3] J.M. Miller, T.R.B. Jones, The mass spectra of azides and halides. In: Suppl.
D: The Chemistry of Halides, Pseudo-Halides, and Azides, Part 1; S. Patai, Z.
Rappoport, Eds.; Wiley: Chichester, 1983; p 75.
[4] W.M.A. Niessen, R.A. Correa C., Interpretation of MS-MS Mass Spectra of
Drugs and Pesticides, Wiley, Hoboken, 2017.
[5] K. Levsen, H.-M. Schiebel, J.K. Terlouw, K.J. Jobst, M. Elend, A. Preiss, H.
Thiele, A. Ingendoh, Even-electron ions: a systematic study of the neutral
species lost in the dissociation of quasi-molecular ions, J. Mass Spectrom.
2007, 42, 1024.
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
8.7 Halogen Compounds
391
Polyhaloalkanes
Fragmentation: Preferred fragmentation of the C–C bond if several halogen atoms
are bonded to one of these carbon atoms. CF 3 (m/z 69) is often the base peak in
terminally perfluorated alkanes, and so is CHCl 2 (m/z 83, 85, 87) in terminally
dichlorinated compounds. Often, X 2 is eliminated besides the usual fragmentation
of X · and HX. Interchange of halogens may occur. For example, m/z 85 (CF 2 Cl) is
a dominant signal (≈ 60%) for CF 3 CFCl 2 .
Ion series: Most fragments are halogenated alkyl and alkenyl groups, easily
detectable on the basis of the isotope signals in the cases of Cl and Br.
Intensities: Intensive peaks mainly in the lower mass range.
Molecular ion: Weak, decreasing with increasing number of halogen atoms. Absent
from the spectra of many polyhalogenated compounds.
Aromatic Halides
Fragmentation: Consecutive losses of halogen radicals and/or acid HX. In
perhalogenated aromatics, decomposition down to C x
+ , with x from 1 to 6 (m/z 12,
24, 36, 48, 60, 72). If alkyl-substituted (C n > 1 ), the base peak is mostly the result of
benzylic cleavage. In an otherwise aromatic environment, m/z 57 is a F indicator
(C 3 H 2 F + ). Elimination of CF 2 (Δm 50) from CF 3 groups attached to the aromatic
ring (from M +· or fragments).
Ion series: Aromatic fragments, C n H n , C n H n-1 , and C n H n-2 (m/z 39, 51–53, 63–65,
75–77, …). In the higher mass range: C n (H,X) n .
Intensities: Dominant peaks in the M +· region.
Molecular ion: Usually very strong. Characteristic isotope signals for Cl and Br.
References
[1] A.G. Loudon, Mass spectrometry and the carbon-halogen bond. In: The
Chemistry of the Carbon-Halogen Bond, Part 1; S. Patai, Ed.; Wiley: London,
1973; p 223.
[2] D.G.I. Kingston, B.W. Hobrock, M.M. Bursey, J.T. Bursey, Intramolecular
hydrogen transfer in mass spectra. III. Rearrangements involving the loss of
small neutral molecules, Chem. Rev. 1975, 75, 693.
[3] J.M. Miller, T.R.B. Jones, The mass spectra of azides and halides. In: Suppl.
D: The Chemistry of Halides, Pseudo-Halides, and Azides, Part 1; S. Patai, Z.
Rappoport, Eds.; Wiley: Chichester, 1983; p 75.
[4] W.M.A. Niessen, R.A. Correa C., Interpretation of MS-MS Mass Spectra of
Drugs and Pesticides, Wiley, Hoboken, 2017.
[5] K. Levsen, H.-M. Schiebel, J.K. Terlouw, K.J. Jobst, M. Elend, A. Preiss, H.
Thiele, A. Ingendoh, Even-electron ions: a systematic study of the neutral
species lost in the dissociation of quasi-molecular ions, J. Mass Spectrom.
2007, 42, 1024.