Ion—Molecule Reactions of [C, H₃, S]⁺ Ions and Evidence for Long-Lived Triplet CH₃S⁺

Abstract

Gas-phase [C, H(3), S](+) ions obtained by electron impact from (CH(3))(2)S at 14 eV undergo two distinct low-pressure ion-molecule reactions with the parent neutral: proton transfer and charge exchange. The kinetics of these reactions studied by Fourier transform ion cyclotron resonance (FT-ICR) techniques clearly suggests the [C, H(3), S](+) species to be a mixture of isomeric ions. While proton transfer is consistent with reagent ions displaying the CH(2)SH(+) connectivity, the observed charge exchange strongly argues for the presence of thiomethoxy cations, CH(3)S(+), predicted to be stable only in the triplet state. Charge exchange reactions are also observed in the reaction of these same [C, H(3), S](+) ions with benzene, toluene and phenetole. For these substrates, the CH(2)SH(+) ions can promote proton transfer and electrophilic methylene insertion in the aromatic ring with elimination of H(2)S. The results obtained for the different substrates suggest that the fraction of long-lived fraction of thiomethoxy cations obtained at 14 eV by electron ionization of dimethyl sulfide amounts to ~(22 -/+ 4)% of the [C, H(3), S](+) fragments.

Gas‐phase electrophilic addition promoted by CH3S+ CH2 ions on aromatic systems

“…Ionization, ion selection, ion–molecule reactions and detection take place in this cell. The general operating conditions of this spectrometer have been previously described in our work related to the identification of triplet state CH 3 S + and C 2 H 5 S + cations 19, 20…”