REACTIVITY OF THE PROTOTYPE ORGANOSULFUR DISTONIC ION - (CH2SH2+)-C-CENTER-DOT

摘要

The intrinsic chemical properties of the prototype organosulfur distonic ion (CH2SH2+)-C-. have been examined in the gas phase in a dual-cell Fourier-transform ion cyclotron resonance mass spectrometer. These studies reveal that the reactivity of the ion (CH2SH2+)-C-. is quite different from that reported recently for the analogous oxygen-containing distonic ion (CH2OH2+)-C-.. Facile deprotonation and hydrogen atom abstraction reactions have been reported for the latter ion. However, reaction of (CH2SH2+)-C-. with neutral molecules often yields the radical cation of the neutral reagent. This reaction likely occurs via deprotonation of the ion followed by other reactions within the collision complex. Collisions with neutral reagents with ionization energies greater than or equal to 9.9 eV can result in base-catalyzed isomerization of the distonic ion to the more stable conventional isomer CH3SH.+. The isomerization is revealed by curved kinetics plots and, at long reaction times, by product ions identical to those observed fur the conventional isomer. At short reaction times, however, the reactivity of the unrearranged distonic ion can be probed. Examination of deprotonation reactions yields a gas-phase proton affinity of less than or equal to 176 kcal mol(-1) for (CH2SH)-C-. at the sulfur atom, In combination with the known heats of formation of H+ and (CH2SH)-C-., the new proton affinity value yields a lower limit of 227 kcal mol(-1) for the heat of formation of (CH2SH2+)-C-.. This value is higher than the previously reported experimental value (219 kcal mol(-1)). [References: 36]