With the help of quantum mechanical methods, the formation of H₂SO₄ by the oxidation of H₂SO₃ with H₂O₂ was studied theoretically. Both stepwise and concerted mechanisms were calculated. It was found that the direct oxidation of H₂SO₃ by H₂O₂ alone requires prohibitive activation energies of >38.6 kcal/mol. However, the addition of one water molecule exhibits a strong catalytic effect that dramatically reduces the overall reaction barrier to 6.2 (2.3 with PCM) kcal/mol. The deprotonated HSO₃^– species also reduces the overall reaction barrier to 5.6 (−5.8 with PCM) kcal/mol. Both of these proceed via concerted pathways. On the other hand, the stepwise mechanisms generally produce intermediates with a hydroperoxy group (−O–O–H), which is a result of a nucleophilic attack by the oxygens of H₂O₂. While studying the catalytic effect of water, a previously unknown hydroperoxy intermediate (HOO)S(OH)₃, where sulfur is coordinated with three OH groups, was found. This work also reveals a rearrangement step of another hydroperoxy intermediate (HOO)SO₂^– to HSO₄^– that was found in earlier experimental studies. For all of the mechanisms calculated, the final H₂SO₄ is formed with a significant exothermicity of >60 kcal/mol. In general, even without sunlight, it was found that the formation of sulfuric acid by hydrogen peroxide can occur in a heterogeneous moisturized environment.

中文翻译：

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H ₂ O ₂在大气中通过H ₂ SO ₃氧化形成硫酸

借助量子力学方法，对H ₂ SO ₃与H ₂ O ₂的氧化作用形成H ₂ SO ₄进行了理论研究。计算了逐步机制和协调机制。已经发现仅H ₂ O ₂就能直接氧化H ₂ SO ₃，要求抑制活化能大于38.6 kcal / mol。但是，添加一个水分子会表现出强大的催化作用，从而将总反应势垒显着降低至6.2（使用PCM时为2.3）kcal / mol。脱质子化的HSO ₃ ^–物种还将总反应势垒降低到5.6 kcal / mol（对于PCM为-5.8）。两者都是通过一致的途径进行的。另一方面，逐步机制通常会产生带有氢过氧基团（-O-O-H）的中间体，这是H ₂ O ₂的氧亲核攻击的结果。在研究水的催化作用时，发现了一个以前未知的氢过氧中间体（HOO）S（OH）₃，其中硫与三个OH基团配位。这项工作也揭示了SO另一个氧化氢的中间体（HOO）的重排步骤₂ ^-向HSO ₄ ^-这是在较早的实验研究发现。对于所有计算的机制，最终的H ₂形成的SO ₄放热度大于60 kcal / mol。通常，即使在没有阳光的情况下，也发现过氧化氢形成硫酸可以在非均质的潮湿环境中发生。