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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Mapping the Kinetic and Thermodynamic Landscape of Formaldehyde Oligomerization under Neutral Conditions
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Mapping the Kinetic and Thermodynamic Landscape of Formaldehyde Oligomerization under Neutral Conditions

机译：中性条件下甲醛低聚的动力学和热力学图谱

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摘要

Density functional theory calculations, including Poisson? Boltzmann implicit solvent and free energy corrections, are applied to study the thermodynamic and kinetic free energy landscape of formaldehyde oligomerization up to the C_4 species in aqueous solution at pH 7. Oligomerization via C?O bond formation leads to linear polyoxymethylene (POM) species, which are the most kinetically accessible oligomers and are marginally thermodynamically favored over their oxane ring counterparts. On the other hand, C?C bond formation via aldol reactions leads to sugars that are thermodynamically much more stable in free energy than POM species; however, the barrier to dimerization is very high. Once this initial barrier is traversed, subsequent addition of monomers to generate trimers and tetramers is kinetically more feasible. In the aldol reaction, enolization of the oligomers provides the lowest energy pathway to larger oligomers. Our study provides a baseline free energy map for further study of oligomerization reactions under catalytic conditions, and we discuss how this will lead to a better understanding of complex reaction mixtures with multiple intermediates and products.
机译：密度泛函理论计算，包括泊松？应用Boltzmann隐式溶剂和自由能校正技术，研究了在pH 7的水溶液中，甲醛低聚至C_4物种的热力学和动能自由能态。它们是动力学上最易接近的低聚物，在热力学上略胜于它们的恶烷环对应物。另一方面，通过醛醇缩合反应形成的C？C键导致糖的热力学自由能比POM物种稳定。然而，二聚化的障碍非常高。一旦越过该初始壁垒，随后添加单体以生成三聚体和四聚体在动力学上更可行。在醛醇缩合反应中，低聚物的烯醇化提供了通往较大的低聚物的最低能量途径。我们的研究提供了基线自由能图，用于进一步研究催化条件下的低聚反应，并且我们讨论了这将如何更好地理解具有多种中间体和产物的复杂反应混合物。

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