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Quantum Chemical Study of the Potential Energy Surface in the Formation of Atmospheric Sulfuric Acid
TaoFu-Ming
Author NameAffiliationE-mail
TaoFu-Ming Department of Chemistry and Biochemistry, California State University, Fullerton, 800 N. State College Blvd. Fullerton, CA 92834, U.S.A. ftao@fullerton.edu 
Abstract:
A new potential energy surface (PES) for the atmospheric formation of sulfuric acid from OH + SO2 is investigated using density functional theory and high-level ab initio molecular orbital theory. A pathway focused in the new PES assumes the reaction to take place between the radical complex SO3·HO2 and H2O. The unusual stability of SO3·HO2 is the principal basis of the new pathway, which has the same final outcome as the current reaction mechanism in the literature but it avoids the production and complete release of SO3. The entire reaction pathway is composed of three consecutive elementary steps, (1) HOSO2 + O2 → SO3·HO2, (2) SO3·HO2 + H2O → SO3·H2O·HO2, (3) SO3·H2O·HO2 → H2SO4 + HO2. All three steps have small energy barriers, under 10 kcal/mol, and are exothermic, and the new pathway is therefore favorable both kinetically and thermodynamically. As a key step of the reactions, step (3), HO2 serves as a bridge molecule for low-barrier hydrogen transfer in the hydrolysis of SO3. Two significant atmospheric implications are expected from the present study. First, SO3 is not released from the oxidation of SO2 by OH radical in the atmosphere. Second, the conversion of SO2 into sulfuric acid is weakly dependent on the humidity of air.
Key words:  Quantum Chemistry, Atmospheric Chemistry, Sulfur Dioxide, Sulfuric Acid, Computational Chemistry, Density Functional Theory, Ab Initio Methods
FundProject:
Quantum Chemical Study of the Potential Energy Surface in the Formation of Atmospheric Sulfuric Acid
TaoFu-Ming
摘要:
A new potential energy surface (PES) for the atmospheric formation of sulfuric acid from OH + SO2 is investigated using density functional theory and high-level ab initio molecular orbital theory. A pathway focused in the new PES assumes the reaction to take place between the radical complex SO3·HO2 and H2O. The unusual stability of SO3·HO2 is the principal basis of the new pathway, which has the same final outcome as the current reaction mechanism in the literature but it avoids the production and complete release of SO3. The entire reaction pathway is composed of three consecutive elementary steps, (1) HOSO2 + O2 → SO3·HO2, (2) SO3·HO2 + H2O → SO3·H2O·HO2, (3) SO3·H2O·HO2 → H2SO4 + HO2. All three steps have small energy barriers, under 10 kcal/mol, and are exothermic, and the new pathway is therefore favorable both kinetically and thermodynamically. As a key step of the reactions, step (3), HO2 serves as a bridge molecule for low-barrier hydrogen transfer in the hydrolysis of SO3. Two significant atmospheric implications are expected from the present study. First, SO3 is not released from the oxidation of SO2 by OH radical in the atmosphere. Second, the conversion of SO2 into sulfuric acid is weakly dependent on the humidity of air.
关键词:  Quantum Chemistry, Atmospheric Chemistry, Sulfur Dioxide, Sulfuric Acid, Computational Chemistry, Density Functional Theory, Ab Initio Methods
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