[C2H4OS]>·>+> Radical cations derived from alkyl thioformates: tandem mass spectrometry and molecular orbital calculations

Abstract

[C₂H₄OS]^˙+ radical cations have been generated upon dissociative ionization of some S-alkyl and O-alkyl thioformates and characterized by tandem mass spectrometry methodologies and molecular orbital calculations at the UQCISD(T)/6-311++G(d,p)//UMP2/6–31G(d,p) level. Use of a combination of collisional activation (high and low energy translational energies), neutralization–reionization and ion–molecule reaction experiments performed in a single instrument, combining different magnetic and electric sectors and a radiofrequency-only quadrupole collision cell, led to the identification of distonic radical cations and ion–molecule complexes such as HC⁺(OH)SCH₂˙ and CH₃S^˙+(H)· · ·CO, beside ions having a more classical structure, HC(S)OCH₃^˙+ and HC(O)SCH₃^˙+. Experimental evidence for the existence of the isomeric distonic HC⁺(SH)OCH₂˙ species has not been found, but calculations of the related [C₂H₄OS]^˙+ potential energy surface suggest that the latter ion is stable and likely to play a role in the fragmentation processes.