Vol. 28, No. 11 (2016)
Compd. No.
Mass Spectrometry of Heterocyclic Compounds: Benzo[b]pyrazolo[3,4-b]-1,6-naphthyridines 2387
TABLE-2
VARIOUS COMMON FRAGMENTS FOR COMPOUNDS 1-9
M
M-H+
M-CO
M-HCN
M-2HCN
Others
1
2
3
4
5
6
7
8
9
312
348, 346
392, 390
392, 390
348, 346
326
348, 346
372
380
311
347, 345
391, 389
391, 389
347, 345
325
347, 345
–
379
284
–
365, 363
365, 363
321, 319
298
321, 319
–
353
–
–
–
–
–
–
–
–
318
–
–
–
321, 319
–
–
–
299
–
–
M-Br
M-Br
–
–
–
–
–
353
Although the most common fragments are collected in the
Table-2. However, a detailed fragmentation scheme is shown
in the following Scheme-II.
CO molecule followed by other fragments, such as halogen (Cl,
Br) or halogen acids (HCl, HBr) and HCN, etc.
ACKNOWLEDGEMENTS
Br
One of the authors (SA) acknowledge an interim Placement
fellowship by HEC, Government of Pakistan.
Br
HN
HN
HN
O
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N
N
N
N
N
N
N
N
N
-HBr
-CO
m/z 28
m/z 80
m/z 282
m/z 362, 364
a
m/z 390, 392
-CN
m/z 26
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-H+
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m/z 27
m/z 256
m/z 255
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m/z 128
m/z 77
Scheme-II
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Fragmentation pattern for compound 3: The fragmen-
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at m/z 392 and 390, which by the loss of a CO (m/z 28) gives
peak at m/z 364 and 362 which further loses HBr molecule
followed by the loss of CN (m/z 26) and gives a peak at m/z
256. It further loses proton and HCN molecule brings to shorter
fragments till a fragment corresponding to a phenyl C6H5 (m/z
77) is given off.
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Conclusion
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In this communication, we have presented a possible mass
fragmentation pattern of a number of benzo[b]pyrazolo[3,4-b]-
1,6-naphthyridines. The fragmentation involves elimination of