Computational study on the mechanism for the gas-phase reaction of dimethyl disulfide with OH

Abstract

The mechanisms for the reaction of CH3SSCH3 with OH radical are investigated at the QCISD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p) level of theory. Five channels have been obtained and six transition state structures have been located for the title reaction. The initial association between CH3SSCH3 and OH, which forms two low-energy adducts named as CH3S(OH)SCH3 (IM1 and IM2), is confirmed to be a barrierless process, The SS bond rupture and HS bond formation of IM1 lead to the products P1(CH3SH + CH3SO) with a barrier height of 40.00 kJ mol−1. The reaction energy of Path 1 is −74.04 kJ mol−1. P1 is the most abundant in view of both thermodynamics and dynamics. In addition, IMs can lead to the products P2 (CH3S + CH3SOH), P3 (H2O + CH2S + CH3S), P4 (CH3 + CH3SSOH), and P5 (CH4 + CH3SSO) by addition-elimination or hydrogen abstraction mechanism. All products are thermodynamically favorable except for P4 (CH3 + CH3SSOH). The reaction energies of Path 2, Path 3, Path 4, and Path 5 are −28.42, −46.90, 28.03, and −89.47 kJ mol−1, respectively. Path 5 is the least favorable channel despite its largest exothermicity (−89.47 kJ mol−1) because this process must undergo two barriers of TS5 (109.0 kJ mol−1) and TS6 (25.49 kJ mol−1). Hopefully, the results presented in this study may provide helpful information on deep insight into the reaction mechanism. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011