Theory of Stereomutation Dynamics and Parity Violation in Hydrogen Thioperoxide Isotopomers 1,2,3 HSO 1,2,3 H

We present quantitative calculations of the mode‐selective stereomutation tunneling and parity violation in chiral hydrogen thioperoxide (‘oxadisulfane') isotopomers XSOY with X, Y=H, D, and T. The torsional tunneling stereomutation dynamics are investigated with a quasi‐adiabatic channel quasi‐harmonic reaction path Hamiltonian approach, which treats the torsional motion anharmonically in detail and all remaining coordinates as harmonic (but anharmonically coupled to the reaction coordinate). We predict how stereomutation is catalyzed or inhibited by excitation of various vibrational modes compared to the corresponding stereomutation dynamics of the vibrational ground state. Parity‐violating potentials were calculated with our recent multiconfiguration linear response (MC‐LR) approach in the random phase approximation (RPA). We find that, in agreement with general scaling expectations, the parity‐violating energy difference for the equilibrium structures of the two HSOH enantiomers ( ca. 5×10 −12 J mol −1 ) is situated intermediate between HOOH and HSSH. Our results on the stereomutation dynamics and the influence of parity violation on these are discussed in relation to investigations for the analogous molecules H 2 O 2 , H 2 S 2 , and Cl 2 S 2 . As expected in XSOY (X, Y=H, D, and T), this influence is much larger than in the corresponding H 2 O 2 isotopomers, but smaller than in H 2 S 2 or Cl 2 S 2 .