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

The mechanisms for the reaction of CH 3 SSCH 3 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 CH 3 SSCH 3 and OH, which forms two low‐energy adducts named as CH 3 S(OH)SCH 3 (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(CH 3 SH + CH 3 SO) 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 (CH 3 S + CH 3 SOH), P3 (H 2 O + CH 2 S + CH 3 S), P4 (CH 3 + CH 3 SSOH), and P5 (CH 4 + CH 3 SSO) by addition‐elimination or hydrogen abstraction mechanism. All products are thermodynamically favorable except for P4 (CH 3 + CH 3 SSOH). 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