Prediction of ^•OH-Initiated and ^•NO₃-Initiated Transformation Products of Polycyclic Aromatic Hydrocarbons by Electronic Structure Approaches

Abstract

The abiotic reaction products of polycyclic aromatic hydrocarbons (PAHs) with hydroxyl radicals ( • OH) and nitrate radicals ( • NO 3 ) are nitro-, oxygen-, and hydroxyl-containing PAHs (NPAHs, OPAHs, and OHPAHs). Four methods of the highest occupied molecular orbital (HOMO), Fukui function (FF), dual descriptor (DD), and population of π electrons (PP-π) are selected to predict the chemical reactivity of PAHs attacked by • OH and • NO 3 in this study. The predicted • OH-initiated and • NO 3 -initiated transformation products are compared with the main PAH transformation products (PAH-TPs) observed in the laboratory. The results indicate that PP-π and DD approaches fail to predict the transformation products of fused PAHs containing five-membered rings. By predicting the PAH-TPs of 13–14 out of the 15 parent PAHs accurately, HOMO and FF methods were shown to be suitable for predicting the transformation products formed from the abiotic reactions of fused PAHs with • OH and • NO 3 .

Photoformation of EPFRs during phototransformation of polycyclic aromatic hydrocarbons (PAHs) on particles in an aqueous solution: The hydrogenation of PAHs and effect of co-existing water matrix factors

“…To further clarify the possible reaction scheme in PAH-Fe(III)-montmorillonite system, various degradation byproducts were detected. Four familiar methods based on the electronic structure of PAHs, such as highest occupied molecular orbital (HOMO) compositions, population of π electrons (pp-π), Fukui function (FF) and dual descriptor (DD) were used to predict the reactivity of PAHs under irradiation and to guide the determination of byproducts (Chen et al, 2022). The structures, relevant numberings and the substitution sites of the reactants were listed in Table S3.…”

Exploring the Chemical Space of the Exposome: How Far Have We Gone?

“…Chemical transformations can take place in the environment (e.g., photo- or biological degradation) or within human-made infrastructures, such as wastewater treatment plants. − Depending on the type of reactions and the structure of the parent compound, there may be more than 100 new chemicals formed at even the first level of the transformation tree. ,, Considering the costs and complexity associated with performing transformation experiments, the expansion of such methods to the exposome chemical space is impossible, Figure . An alternative to this experimentally driven approach has been the predictive models where a combination of machine learning and heuristic methods are used. ,, However, these methods are very uncertain, opaque, are limited to a few reaction pathways while stopping at shallow levels (e.g., first or second levels) in the transformation tree. , This implies that our current estimates of the coverage of the exposome chemical space are orders of magnitude smaller than its true size, given the number of possible reactions.…”

“…Chemical transformations can take place in the environment (e.g., photo- or biological degradation) or within human-made infrastructures, such as wastewater treatment plants. 30 − 33 Depending on the type of reactions and the structure of the parent compound, there may be more than 100 new chemicals formed at even the first level of the transformation tree. 31 , 34 , 35 Considering the costs and complexity associated with performing transformation experiments, the expansion of such methods to the exposome chemical space is impossible, Figure 1 .…”