Potential Energy Curves for Formation of the CH2O2 Criegee Intermediate on the 3CH2 + 3O2 Singlet and Triplet Potential Energy Surfaces,The Journal of Physical Chemistry A

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Potential Energy Curves for Formation of the CH2O2 Criegee Intermediate on the 3CH2 + 3O2 Singlet and Triplet Potential Energy Surfaces
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2019-10-04 , DOI: 10.1021/acs.jpca.9b07368
Sandhiya Lakshmanan ₁ , Rene F. K. Spada , Francisco B. C. Machado , William L. Hase ₁

Affiliation

The potential energy curves (PECs) for the interaction of ³CH₂ with ³O₂ in singlet and triplet potential energy surfaces (PESs) leading to singlet and triplet Criegee intermediates (CH₂OO) are studied using electronic structure calculations. The bonding mechanism is interpreted by analyzing the ground state multireference configuration interaction (MRCI) wave function of the reacting species and at all points along the PES. The interaction of ³CH₂ with ³O₂ on the singlet surface leads to a flat long-range attractive PEC lacking any maxima or minima along the curve. The triplet surface stems into a maximum along the curve resulting in a transition state with an energy barrier of 5.3 kcal/mol at CASSCF(4,4)/cc-pVTZ level. The resulting ³CH₂OO is less stable than the ¹CH₂OO. In this study, the biradical character (β) is used as a measure to understand the difference in the topology of the singlet and triplet PECs and the relation of the biradical nature of the species with their structures. The ³CH₂OO has a larger biradical character than ¹CH₂OO, and because of the larger bond order of ¹CH₂OO, the C–O covalent bond becomes harder to break, thereby stabilizing ¹CH₂OO. Thus, this study provides insights into the shape of the PEC obtained from the reaction between ³CH₂ and ³O₂ in terms of their bonding nature and from the shape of the curves, the temperature dependence or independence of the rate of the reaction is discussed.

中文翻译：

在³ CH ₂ + ³ O ₂单重态和三重态势能面上形成CH ₂ O ₂激昂中间体的势能曲线

使用电子结构计算研究了导致单重态和三重态Criegee中间体（CH ₂ OO）的单重态和三重态势能表面（PES）中³ CH ₂与³ O ₂相互作用的势能曲线（PECs）。通过分析反应物种以及沿PES的所有点的基态多参考构型相互作用（MRCI）波函数来解释键合机理。³ CH ₂与³ O ₂的相互作用单线态表面上的“ P”导致平坦的远程有吸引力的PEC沿曲线缺少任何最大值或最小值。三重态表面沿曲线最大，从而导致过渡态，在CASSCF（4,4）/ cc-pVTZ水平上的能垒为5.3 kcal / mol。所得的³ CH ₂ OO比¹ CH ₂ OO不稳定。在这项研究中，使用双自由基特征（β）作为了解单线态和三线态PEC拓扑结构差异以及该物种的双自由基性质与其结构之间关系的一种量度。的³ CH ₂ OO具有较大的双基字符大于^1个CH ₂OO，并且由于¹ CH ₂ OO的键序较大，因此C–O共价键变得更难以断裂，从而稳定了¹ CH ₂ OO。因此，本研究从³ CH ₂和³ O ₂之间的键合性质以及曲线的形状提供了对从³ CH ₂和³ O ₂之间的反应获得的PEC形状的认识，温度依赖性或反应速率的独立性是讨论过。

更新日期：2019-10-05

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