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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Mechanism of the Atmospheric Reaction between the Radical CH_3SCH_2 and O_2
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Mechanism of the Atmospheric Reaction between the Radical CH_3SCH_2 and O_2

机译：自由基CH_3SCH_2与O_2的大气反应机理。

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In this article, the mechanism of the reaction between the atmospheric CH_3SCH_2 radical and O_2 molecule was studied using an ab initio correlated level of theory. We have performed geometry optimizations at the UMP2/6-31G(d) level of theory and used the additivity approximation to obtain the activation energy at the UCCSD(T)/6-311+G(2df,2p) level. The obtained activation energy is -3.31 kcal/mol. The CH_3SCH_2O_2 radical has three possible conformations, named P1, P2, and P3. However, the conformer formed in the addition reaction, P1, is not the most stable. The transition states to interconvertion between the three conformers were optimized and the rate constants for these reactions were calculated, as well as the exothermicities of each one. These values allowed us to conclude that, in the equilibrium, the distribution of these conformers will be 71% of P2 and 29% of P1. We have used this distribution to obtain a weight average to the exothermicity of the reaction between the CH_3SCH_2 radical and O_2, which is -26.19 kcal/mol. The heat of formation for the mixture of the two conformers of the CH_3SCH_2O_2 radical was also determined as 6.51 kcal/mol. The reaction free energy was calculated as -15.68 kcal/mol, considering that distribution.
机译：本文采用从头算的相关理论研究了大气中CH_3SCH_2自由基与O_2分子反应的机理。我们已经在理论上的UMP2 / 6-31G（d）级别上进行了几何优化，并使用了加和近似来获得UCCSD（T）/ 6-311 + G（2df，2p）级别的激活能。所获得的活化能为-3.31kcal / mol。 CH_3SCH_2O_2基具有三个可能的构型，分别称为P1，P2和P3。然而，在加成反应中形成的构象异构体P1不是最稳定的。优化了三个构象体之间的相互过渡转变状态，并计算了这些反应的速率常数，以及每个反应的放热度。这些值使我们可以得出结论，在平衡状态下，这些构象异构体的分布将为P2的71％和P1的29％。我们已经使用该分布来获得CH_3SCH_2自由基与O_2之间反应的放热的重均值，为-26.19 kcal / mol。 CH_3SCH_2O_2自由基的两个构象异构体的混合物的形成热也确定为6.51 kcal / mol。考虑到该分布，反应自由能计算为-15.68kcal / mol。

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