Mass Spectral Study of Some Phenyl-mono and Dinitropyridyl Sulfide, Ether, Amine and Sulfone Derivatives

Abstract

The electron impact ionization of some mono-and dinitropyridylphenylsulfiede, ether, amine and sulfone derivatives were studied at 70 eV energy. All the 8 compounds studied underwent ring closure during the formation of a carbazole radical cation as a general feature in their mass spectra. The basic differences in the mass spectral behaviour are mainly attributed to the position of the nitro group in the pyridyl ring and the fragmentation pathway is directed by the sulfur, oxygen or nitrogen moiety. The base peak in the mass spectra is determined by such differences.

Tandem mass spectrometry of some nitropyridylaryl sulfides

“…In addition, two more low abundance fragment ions, [M − 31] + and [M − R − 58] + , at m/z 173 are present in the mass spectra of series I, Table 1. The [M − 31] fragment is presumably due to molecular ion rearrangement followed by HNO · loss forming substituted benzo[5,6][1,4]oxathiino[3,2‐ b ]pyridine radical ion in a similar manner to that discussed earlier 10. The second could be formed through the stepwise expulsion of CNO 2 and R 3 radicals to produce a benzothienopyrrole fragment ion at m/z 173, Scheme .…”

“…The facile formation of the fragment ion peak at m/z 139 (corresponding to C 5 N 2 OSH 3 ) as a base peak in most of these series via molecular ion rearrangement and C‐S cleavage is presumably an indication for the ortho ‐effect 1,. 10…”

“…Different mechanistic pathways have been reported to account for the fragmentation processes in mass spectrometric studies of o ‐dinitrodiaryl amines5,, 6 and of ether,7 sulfide,8,, 9 sulfoxide10 and sulfone10 derivatives of nitroaryl compounds. All of these proposed mechanisms involve either skeletal rearrangment, i.e.…”

“…a ring closure via expulsion of HNO 2 from the molecular ion, or successive losses of OH · , NO · , HNO · and NO 2 · . The proposed mechanisms for HNO 2 elimination are highly favoured in cases where the ortho ‐effect1,, 5,, 10–13 can be expected to operate.…”