Theoretical determination of the properties of Methanesulfinic and Methanesulfonic acids

Abstract

As propriedades estruturais, espectroscópicas e termodinâmicas de duas espécies de enxofre de interesse atmosférico, ácidos metanosulfínico (CH 3 S(O)OH, MSIA) e metanosulfônico (CH 3 S(O) 2 OH, MSA) foram determinadas no nível de CCSD(T)/CBS (coupled-cluster with single and double and perturbative triple excitations/complete basis set) de teoria. Duas conformações foram encontradas para o ácido metanosulfínico e o valor médio determinado para a entalpia de formação foi -337,2 kJ mol -1 . Para o ácido metanosulfônico, o resultado para a entalpia de formação foi 566,2 kJ mol -1 . Escolhendo cuidadosamente as reações químicas e considerando a existência de duas conformações de MSIA, esta investigação reporta os valores mais precisos de DH f disponíveis até agora para estas espécies.The structural, spectroscopic and thermochemical properties of two sulfur species of atmospheric interest, methanesulfinic (CH 3 S(O)OH, MSIA) and methanesulfonic (CH 3 S(O) 2 OH, MSA) acids, were determined at the CCSD(T)/CBS (coupled-cluster with single and double and perturbative triple excitations/complete basis set) level of theory. Two stable conformers were found to the methanesulfinic acid, and the determined average value for the enthalpy of formation (DH f ) was -337.2 kJ mol -1 . For methanesulfonic acid, the determined enthalpy of formation was 566.2 kJ mol -1 . By carefully choosing of the chemical reactions and considering the existence of two MSIA conformers, this investigation reports the most accurate DH f values available to date for these species. Keywords: dimethyl sulfide, enthalpy of formation, CCSD(T)/CBS theory IntroductionDimethyl sulfide (DMS), generated in the ocean by phytoplankton, is an important natural source of sulfur in the atmosphere. 1 The main final products of its atmospheric decomposition are sulfuric acid and sulfate ions, which are key species in the climate regulation, due to the fact that they are precursors of aerosols. Sulfur aerosols act in the global warming producing a negative radiative forcing, dispersing the solar radiation and increasing the albedo. 2 Besides, due to the low gas pressure and polarity, these species can act as cloud condensation nuclei (CCN), condensing water molecules. 3,4 Several experimental and theoretical investigations of the oxidation of DMS in gas phase were conducted 5-7 and studies for OH-initiated reaction had revealed methanesulfonic acid (CH 3 S(O) 2 OH, MSA) 8 and methanesulfinic acid (CH 3 S(O) OH, MSIA) 9 as two key intermediates. In general, there are some difficulties in the characterization of the products, and the values of product yields reported can differ significantly. It is generally accepted that MSA is produced from the OH addition to DMS, in a mechanism highly dependent on temperature and O 2 partial pressure. On the other hand, the presence of MSIA in the atmospheric decomposition of DMS was proposed by Yin et al., 10 as a second-generation product of the DMS oxidation. However, the mechanism and the yields of MSIA formation were reasons of ...

A comparative molecular dynamics study of sulfuric and methanesulfonic acids

“…For MSA, these results agree well with the structural parameters previously obtained by other authors. [16][17][18]34 It is important to notice, that according to Durig et al, 16 we have analyzed the gauche OH group configuration. In this geometric arrangement, which correspond to a local minimum, the hydrogen atom quasieclipses one of the oxygen atoms.…”

“…In this geometric arrangement, which correspond to a local minimum, the hydrogen atom quasieclipses one of the oxygen atoms. Moreover, according to these authors, [16][17][18] the CH 3 group conformation is staggered. For SA the simulation results show a good agreement with the experimental findings of Kuczkoswki et al 46 (see Fig.…”

“…Some ab initio studies of pure MSA have been implemented to calculate enthalpies of formation, structures and spectroscopic properties. [16][17][18] The same methodology has been used to analyze the structure and the energy of hydrated MSA clusters, and to investigate the influence of the hydrogen bond network in the polarizabilities of the molecules. [19][20][21] Finally, MD simulations of pure MSA 22 and MSA-water mixtures 23 have also been performed.…”

Methanesulfonyl Iodide

“…Calculations were also performed on CH 3 SO 2 H, I 2 , and HI. The optimized structure for CH 3 SO 2 H(g) has a H−O−S−O dihedral angle of 169°, which corresponds to the species MSIA1 calculated by Carvalho et al 16 Gibbs energies calculated for the various species are summarized in Table 5.…”

Theoretical Study of Alkylsulfonic Acids: Force-Field Development and Molecular Dynamics Simulations

“…Ab initio methods have been employed to study physicochemical properties of MSA, such as conformations, heat of formation, and reaction energetics, in the gas phase. , Structure and energetics of MSA–water clusters and other MSA mixtures have also been investigated. − Although ab initio simulation methods offer the most accurate computational approach with direct access to electronic structural properties, their high computational cost places a significant restriction on their applications. Therefore for large systems, especially solution-phase systems that require extended simulations, classical methods couched in force fields still provide a very useful approach.…”