N
X
C
Hal
O
N
S
P Si
Natural
Products
Solvents
C
C
C
C C
C
8.9 Nitrogen Compounds
405
8.9.3 Diazo Compounds and Azobenzenes
Diazo Compounds [4,5]
Diazonium: Because of the low volatility of diazo compounds, their electron impact
mass spectra show thermal decomposition products. These are formed by loss of
N 2 (e.g., a diazonium chloride gives rise to the corresponding aromatic chloro
compound). From a phenyl diazonium ortho-carboxylate zwitterion, biphenylene is
formed as dimerization product.
Diazomethane and derivatives: M +· is strong except when catalytic decomposition
occurs on metal surfaces of the inlet system. Loss of N 2 is a dominant reaction of
diazomethane and diazoketones.
Azobenzenes
Fragmentation: Cleavage at the azo group followed by loss of N 2 , giving rise to the
dominant base peak.
ESI-MS/MS: N 2 elimination (Δm 28) from [M+H] + .
Ion series: Aromatic fragments (C n H n , C n H n±1 ; m/z 39, 51–53, 63–65, 75–77, …).
Intensities: Dominant M +· and azo cleavage products.
Molecular ion: Strong.
8.9.4 Azides
Aliphatic Azides [6]
Fragmentation: [M-42] + (N 3
· elimination) or [M-28] +· (N 2 elimination) dominant in
most cases. The spectra are similar to those of the corresponding aliphatic compounds.
Ion series: Aliphatic hydrocarbon series.
Intensities: Dominant peaks in the lower mass range, as in aliphatic compounds.
Molecular ion: Absent or weak.