ION-MOLECULE REACTION OF PYRIDINE WITH CS3 RADICAL CATIONS - EXPERIMENTAL-EVIDENCE FOR THE PRODUCTION OF PYRIDINE N-THIOXIDE DISTONIC IONS

Chemical ionization of pyridine using carbon disulphide as the reagent gas leads to the formation of new distonic ions, pyridine N-thioxide radical cations, 2(+.). The origin of these ions is unambiguously attr ibuted to the reaction of CS3+. ions with neutral pyridine owing to th e use of a new hybrid mass spectrometer combining sectors and an r.f.- only quadrupole collision cell Boated at a voltage similar to the acce lerating voltage of the ions. Collisional activation (CA) of appropria te reference ions (the molecular ions of isomeric mercaptopyridines, 4 -6(+.)) demonstrates the actual structure of the ions, while neutraliz ation-reionization experiments indicate the stability of the correspon ding neutral dipole in the gas phase. Several reactions were performed in the quadrupole collision cell with molecules recognized as excelle nt trapping reagents of distonic ions: dimethyl disulphide, dimethyl d iselenide and nitric oxide. The 2(+.) ions react with nitric oxide gen erating NOS+ ions; this reaction is not observed for the reference 4-6 (+.) ions. Although the transfer of thiomethlyl radicals or selenometh yl radicals is observed for all the radical cations, the resulting [2( 4-6) + S(Se)](+) cations are clearly differentiated by CA. It is also shown that the transfer of S+. to perdeuterated pyridine is a specific reaction of the distonic 2(+.) ions. (C) 1997 John Wiley & Sons, Ltd.