Abstract

A comparative analysis of the reactivity indices of the model structure of humic acids (HAs) and a number of antioxidants was carried out based on the results of quantum-chemical calculations performed using the density functional theory (DFT) b3lyp/6-31g(d,p) method. With the use of 15 compounds as an example, it was found that the electronegativity index χ linearly correlates with the energy of the lowest unoccupied molecular orbital (E_LUMO), R² = 0.977. HAs (E_LUMO = –2.52) are located close to molecular oxygen (E_LUMO = –3.07), and this fact indicates a high electronegativity of these natural compounds. It was proposed to evaluate the antioxidant ability of the organic matter of HAs by the adsorption energy of molecular oxygen. By determining the local minima of O₂ sensing energy in different sections of HAs using the pm6 quantum chemical method, it was established that oxygen is adsorbed by a hydroxyl group with the energy ∆E_ads = –70 kcal/mol. This allows the highly reactive organic part of HAs to inhibit molecular oxygen in oxidation processes.

中文翻译：

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腐植酸氧化还原性质的量子化学预测

摘要

基于使用密度泛函理论（DFT）b3lyp / 6-31g（d）进行的量子化学计算结果，对腐殖酸（HAs）和多种抗氧化剂的模型结构的反应性指数进行了比较分析。 ，p）方法。以15种化合物为例，发现电负性指数χ与最低未占据分子轨道（E _LUMO）的能量线性相关，R ² = 0.977。HA（E _LUMO = –2.52）位于分子氧附近（E _LUMO= –3.07），这一事实表明这些天然化合物具有高电负性。提出了通过分子氧的吸附能来评价HAs有机物的抗氧化能力。通过使用pm6量子化学方法确定HA的不同部分中O ₂感应能量的局部最小值，可以确定氧被羟基吸附的能量为∆ E _ads = –70 kcal / mol。这使得HAs的高反应性有机部分能够抑制氧化过程中的分子氧。