Thermokinetic proton transfer and ab initio studies of the [2H,S,O](+) system. The proton affinity of HSO

The [2H,S,O](+) ionic system has been studied jointly with a selected ion f low tube (SIFT) and by coupled cluster ab initio methods. Experimentally, t he [2H,S,O](+) ions were generated by the reaction of SO+(X (2)Pi(r)) with C2H6, and reacted at room temperature with CH,SH. n-C3H6, HCO2H, o-C6H4F2, CF3C(O)CH3, CH2O, H2S, C-C6H12, CS2, C2H4, and SO2 comprising a series of r eference bases with gas basicities ranging from 177 to 154 kcal mol(-1). Th ermokinetic analysis of the proton-transfer efficiencies in these reactions yields a free energy of proton detachment of 163.6 +/- 2.2 kcal mol(-1) fo r HSOH+. The results of the ab initio study are used to determine the relat ionship of this proton detachment energy to the various isomeric Terms of [ 2H,S,O](+) and the two isomers HSO and SOH. The resulting best values for t he gas-phase basicity and the proton affinity of HSO at 298 K are 163.6 (+4 .6, -2.2) kcal mol(-1) and 171.0 (+4.6, -2.4) kcal mol(-1), respectively. O bservation of the charge-transfer behavior of HSOH+ with the selected neutr al bases restricts the recombination energy of HSOH+ to the range 9.5 +/- 0 .2 eV. Rate coefficients and product distributions for the reactions of HSO H+ with the bases in the bracketing study are presented and discussed, as w ell as the results of the ab initio study and the interpretation of the the rmokinetic data. Additionally, a revised determination of the gas-phase bas icity, proton affinity, and enthalpy of formation of HS2 at 298 K (from the proton-transfer reactions of HSSH+) is presented, which increases those qu antities by 0.8 kcal mol(-1) to 170.6 +/- 2.2, 178.8 +/- 2.4, and 25.8 +/- 2.5 kcal mol(-1), respectively.