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

Abstract

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 kH2S+OH=1.35×10-19T2.5exp(1014/T) over the temperature range 228–591K, and the rate constant is 6.24×10−12cm3molecule−1s−1 at 298K, which are consistent with the experimental values. For the X-assisted reactions, the rate constants are increasing gradually from 3.56×10−16 at 228K to 1.57×10−13cm3molecule−1s−1 at 591K in the presence of one water, while the rate constant is only 3.36×10−17 or 1.16×10−20cm3molecule−1s−1 for water dimer or one H2S molecule assisted reaction at 298K, which indicates that the presence of X will not play an important role in the oxidation of H2S by OH radicals under atmospheric conditions.