Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy.
Dipartimento di Chimica, Università degli Studi di Torino, Via Pietro Giuria 5, 10125 Torino, Italy.
Molecules. 2021 Apr 27;26(9):2550. doi: 10.3390/molecules26092550.
Aromatic nitroderivatives are compounds of considerable environmental concern, because some of them are phytotoxic (especially the nitrophenols, and particularly 2,4-dinitrophenol), others are mutagenic and potentially carcinogenic (e.g., the nitroderivatives of polycyclic aromatic hydrocarbons, such as 1-nitropyrene), and all of them absorb sunlight as components of the brown carbon. The latter has the potential to affect the climatic feedback of atmospheric aerosols. Most nitroderivatives are secondarily formed in the environment and, among their possible formation processes, photonitration upon irradiation of nitrate or nitrite is an important pathway that has periodically gained considerable attention. However, photonitration triggered by nitrate and nitrite is a very complex process, because the two ionic species under irradiation produce a wide range of nitrating agents (such as NO, HNO, HOONO, and HOONO), which are affected by pH and the presence of organic compounds and, in turn, deeply affect the nitration of aromatic precursors. Moreover, aromatic substrates can highly differ in their reactivity towards the various photogenerated species, thereby providing different behaviours towards photonitration. Despite the high complexity, it is possible to rationalise the different photonitration pathways in a coherent framework. In this context, this review paper has the goal of providing the reader with a guide on what to expect from the photonitration process under different conditions, how to study it, and how to determine which pathway(s) are prevailing in the formation of the observed nitroderivatives.
芳香族硝基衍生物是一类备受关注的环境化合物，因为其中一些具有植物毒性（特别是硝基酚，尤其是 2,4-二硝基酚），另一些具有致突变性和潜在致癌性（例如多环芳烃的硝基衍生物，如 1-硝基芘），而且它们全部作为棕色碳的组成部分吸收阳光。后者有可能影响大气气溶胶的气候反馈。大多数硝基衍生物是在环境中次生形成的，在它们可能的形成过程中，硝酸盐或亚硝酸盐照射下的光硝化作用是一个重要的途径，它周期性地引起了相当大的关注。然而，硝酸盐和亚硝酸盐引发的光硝化作用是一个非常复杂的过程，因为在照射下，这两种离子物种会产生广泛的硝化剂（如 NO、HNO、HOONO 和 HOONO），这些硝化剂受 pH 值和有机化合物的存在影响，进而深刻影响芳香族前体的硝化作用。此外，芳香族底物在与各种光生物质的反应性方面可能存在很大差异，从而对光硝化作用表现出不同的行为。尽管存在高度复杂性，但可以在一个连贯的框架内合理化不同的光硝化途径。在这方面，本文的目的是为读者提供一个指南，了解在不同条件下光硝化过程的预期结果、如何研究它以及如何确定观察到的硝基衍生物形成过程中的主要途径。
