The effect of (H2O)n (n=1-2) or H2S on the hydrogen abstraction reaction of H2S by OH radicals in the atmosphere

The hydrogen abstraction reaction mechanisms of H2S with OH radicals without and with catalyst X (X = H2O, (H2O)(2), or H2S) have been investigated at the CCSD(T)/6-311++G(3df,3pd)//BH&HLYP/6-311++ G(3df,3pd) levels of theory, coupled with reaction kinetics calculations by using conventional transition state theory. For the reaction without catalyst, the temperature dependence of the rate coefficients is given as k(H2S+OH) = 1.35 x 10(-19)T(2.5) exp(1014/T) over the temperature range 228-591 K, and the rate constant is 6.24 x 10(-12) cm(3) molecule(-1) s(-1) 298 K, which are consistent with the experimental values. For the X-assisted reactions, the rate constants are increasing gradually from 3.56 x 10(-16) at 228 K to 1.57 x 10(-13) cm(3) molecule(-1) s(-1) at 591 K in the presence of one water, while the rate constant is only 3.36 x 10(-17) or 1.16 x 10(-20) cm(3) molecule(-1) s(-1) for water dimer or one H2S molecule assisted reaction at 298 K, which indicates that the presence of X will not play an important role in the oxidation of H2S by OH radicals under atmospheric conditions. (C) 2015 Elsevier B.V. All rights reserved.