Atmospheric Sulfur Compounds In Several Chemical Reaction Mechanism And Kinetic Studies

Sulfur compounds play an important role in the atmospheric and environmental chemistry. Important anthropogenic sources include fossil fuel combustion, coal refining as well as automobiles, chemical industry, such as SO₂,H₂S , OCS, CS₂ are all hurtful for human and environment.. Dimethyl Sulfide (CH₃SCH₃, DMS), which produced by marine phytoplankton, is the most important reduced sulfur compound emitted from the ocean into the atmosphere. It has been proposed that the oxidation of DMS in the atmosphere could play an important role in climate modification because several products from DMS oxidation are highly non-volatile and could participate in particle formation and growth processes, thus affecting the albedo of the atmosphere and the solar radiation budget at the Earth's surface。 So study of mechanism and kinetics nature for sulfides'oxidation in atmosphere is important theoretical and practical meaning for understandings sulfides'formation and pollution。The study of the microcosmic reaction mechanisms and macroscopic overall reaction rate constants has always been the leading subjects in Chemical reaction Kinetics, and mechanism and dynamics research of the gas phase molecule multi-channel reaction has been a grand challenge for theoretical chemist. In this thesis, many important reactions involved in the sulfides' oxidation processes have been studied using ab initio and canonical variational transition state. The important and value results in this thesis can be summarized as follows:1. The reactions of DMS and nitrogen oxygen chemical compound (NO_x) (X=l,2,3)The reactions of DMS and nitrogen oxygen chemical compound (NO_x) have been studied systematically for the first time. The potential energy surface(PES)for the DMS+NO_x systems were calculated at the QCISD(T)//MP2/ 6-311++G^** level, theoretical analysis provided conclusion evidence that the main process occurring in each case is the H abstraction from C-H(in methyl) bonds; the other reactions are difficult to react for the higher barriers.On the basis of the ab initio data, the kinetics calculations for the three reaction have been deduced using canonical variational transition state theory (CVT) with small-curvature tunneling correction method (SCT) over the temperature range of 200-3000 K. Studies show: in the reaction of the NO₃ with DMS, the total rate constants is nearly equal to the rate...