[C2H4OS](center dot+) radical cations derived from alkyl thioformates: tandem mass spectrometry and molecular orbital calculations

[C2H4OS](.+) radical cations have been generated upon dissociative ionizati on of some S-alkyl and O-alkyl thioformate sand characterized by tandem mas s spectrometry methodologies and molecular orbital calculations at the UQCI SD(T)/6-311 + +G(d,p)//UMP2/6-31G(d,p) level. Use of a combination of colli sional activation thigh and low energy translational energies), neutralizat ion-reionization and ion-molecule reaction experiments performed in a singl e instrument, combining different magnetic and electric sectors and a radio frequency-only quadrupole collision cell, led to the identification of dist onic radical cations and ion-molecule complexes such as HC+(OH)SCH2. and CH 3S.+(H) - CO, beside ions having a more classical structure, HC(=S)OCH3.+ a nd HC(=O)SCH3.+. Experimental evidence for the existence of the isomeric di stonic HC+(SH)OCH2. species has not been found, but calculations of the rel ated [C2H4OS](.+) potential energy surface suggest that the latter ion is s table and likely to play a role in the fragmentation processes.