Computational studies of the potential energy surface for O(1<i>D</i>)+H2S: Characterization of pathways involving H2SO, HOSH, and H2OS

Abstract

Structures and vibrational frequencies for minima and transition states on the O(1D)+H2S potential energy surface have been characterized at the unrestricted second-order Mo/ller–Plesset (UMP2)=full/6-31G(d) level. The results for the thioperoxide HOSH agree with experimental IR spectra. Gaussian-2 theory was employed to calculate ΔHf,298 for HOSH of −119.3 kJ mol−1, −47.1 kJ mol−1 for the sulfoxide H2SO, and 47.0 kJ mol−1 for the thiooxonium ylide H2OS. We also derived ΔHf,0 for HOS and HSO of −2.7 and −17.0 kJ mol−1, respectively. Comparisons with ΔHf for known asymptotes on the potential energy surface gave good agreement, except in the case of HSO. Rice–Ramsperger–Kassel–Marcus (RRKM) analysis suggests that in most environments, except at low pressures and temperatures, H2OS will be short lived, and rate constants for isomerization of the three bound adducts under thermally equilibrated conditions are derived. The potential energy surface is discussed in the context of single-collision experiments, and pathways leading to SH+OH, 1SO+H2, HSO+H, HOS+H, and 1S+H2O have been analyzed.