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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Reversal of the Relative Stability of the Isomeric Radicals HSO and HOS upon Hydration and Their Reactions with Ozone
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Reversal of the Relative Stability of the Isomeric Radicals HSO and HOS upon Hydration and Their Reactions with Ozone

机译：水合过程中异构自由基HSO和HOS的相对稳定性的逆转及其与臭氧的反应

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摘要

The radical HSO is an oxidation product of pollutants such as H2S and CH3SH in Earth’s atmosphere. For the first time, the interaction of HSO and its tautomer HOS with single water molecules to yield the hydrates HSO· nH2O and HOS· nH2O was studied for n ) 1-3, applying the high-level G3X(MP2) theory. A large number of structures corresponding to local minima on the potential energy surfaces has been identified. While gaseous HSO is more stable than HOS, the enthalpy diffference between HSO· nH2O and HOS· nH2O decreases with increasing degree of hydration and becomes practically zero for n ) 3. Thus, in aqueous solution as well as in fog and rain droplets, HOS is expected to compete with HSO. The barrier for the tautomerization of HSO to HOS is dramatically lowered by the presence of water molecules since a cyclic transition state allows a concerted proton shift within the system of neighboring hydrogen bonds. The corresponding activation enthalpy of only 73.5 kJ mol-1 predicted for the transformation of HSO·2H2O into HOS·2H2O may be compared to the 202 kJ mol-1 reported for the tautomerization of the unhydrated gaseous HSO/HOS molecules. The impact of water of hydration on the fundamental vibrational modes of HSO and HOS has also been studied. Furthermore, HOS is predicted to dimerize at low temperatures to give two van der Waals molecules with singlet (symmetry C2) or triplet configuration (symmetry C2h), the latter being more stable than the singlet isomer. The disproportionation of 2HSO to H2S and SO2 is predicted to be exothermic by -263.5 kJ mol-1. The reaction of HSO with ozone to HSO2 and O2 is also strongly exothermic by -274.0 kJ mol-1 and seems to proceed without any barrier. HOS forms a 1:1 van der Waals complex with O3; the redox reaction of its two components is calculated as exothermic by -410.9 kJ mol-1 and results in a rather stable adduct between HOSO and O2 with the structure of a peroxo isomer of HOSO3. This unprecedented hydrogen peroxosulfite radical might open a novel route to atmospheric sulfate without the intermediate formation of SO2 and SO3.
机译：自由基HSO是地球大气中H2S和CH3SH等污染物的氧化产物。首次使用高水平的G3X（MP2）理论研究了n）1-3中HSO及其互变异构体HOS与单个水分子的相互作用以生成水合物HSO·nH2O和HOS·nH2O。已经确定了大量对应于势能表面上局部极小值的结构。虽然气态的HSO比HOS稳定，但是HSO·nH2O和HOS·nH2O之间的焓差随水合度的增加而减小，并且对于n）3几乎变为零。因此，在水溶液以及雾状和雨滴状中，HOS有望与HSO竞争。由于水分子的存在，HSO互变异构化成HOS的壁垒大大降低，因为循环过渡态允许相邻氢键系统内的质子协同移动。可以将预期的HSO·2H2O转化为HOS·2H2O的相应活化焓仅为73.5 kJ mol-1与报告的202 kJ mol-1的无水气态HSO / HOS分子互变异构化进行比较。还研究了水合水对HSO和HOS基本振动模式的影响。此外，据预测，HOS将在低温下二聚化，从而产生两个具有单线态（对称性C2）或三线态构型（对称性C2h）的范德华分子，后者比单线态异构体更稳定。预测-263.5 kJ mol-1将2HSO歧化为H2S和SO2放热。 HSO与臭氧对HSO2和O2的反应也被-274.0 kJ mol-1强烈放热，并且似乎没有任何障碍地进行。 HOS与O3形成1：1 Van der Waals配合物;通过-410.9 kJ mol-1放热计算出其两种组分的氧化还原反应，并导致HOSO和O2之间形成具有HOSO3过氧化物异构体结构的相当稳定的加合物。这种前所未有的过亚硫酸氢根自由基可能会打开一条通往大气中硫酸盐的新途径，而不会中间形成SO2和SO3。

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