Beijing Key Laboratory of Environmental and Viral Oncology, College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100124, China.
Environ Sci Process Impacts. 2021 Mar 1;23(3):480-490. doi: 10.1039/d0em00476f. Epub 2021 Feb 17.
Aliphatic amines as common constituents of dissolved organic nitrogen (DON) exhibit high reactivity during ozonation; however, our understanding of their degradation mechanisms is very limited. In this study, methylamine (MA) and ethylamine (EA), as well as their secondary and tertiary amines (DMA, DEA, TMA and TEA) were chosen as aliphatic amine models and their degradation mechanisms during ozonation were investigated by using the DFT method. The oxygen-transfer reaction occurs initially and rapidly in the ozonation of all the above amines with a ΔG value of 8-10 kcal mol in great agreement with the experimental rate constant of 10 to 10 M s. Moreover, N-oxide as the main degradation product for tertiary amines directly forms after oxygen-transfer, while nitroalkanes as main products for secondary and primary amines are yielded after a series of reactions mediated by hydroxylamine and nitrosoalkane with a ΔG value of 10-13 kcal mol. Regarding the minor N-dealkylated products for all amines, alkylamino alcohol is an important intermediate possibly generated via a radical reaction pathway with a ΔG value of 21-34 kcal mol. Additionally, comparison of the reactivity of aliphatic amines, hydroxylamines and alkylamino alcohols with ozone was made and elucidated in this study. The results are expected to expand our understanding of the degradation mechanisms for nitrogenous compounds during ozonation.
脂肪胺作为溶解态有机氮（DON）的常见成分，在臭氧化过程中表现出很高的反应活性；然而，我们对其降解机制的理解非常有限。在本研究中，选择甲胺（MA）和乙胺（EA）以及它们的仲胺和叔胺（DMA、DEA、TMA 和 TEA）作为脂肪胺模型，通过 DFT 方法研究了它们在臭氧化过程中的降解机制。在上述所有胺的臭氧化中，氧转移反应首先迅速发生，ΔG 值为 8-10 kcal mol，与实验速率常数 10 到 10 M s 非常吻合。此外，N-氧化物作为叔胺的主要降解产物直接在氧转移后形成，而仲胺和伯胺的主要产物硝基烷烃则是在羟胺和亚硝烷介导的一系列反应后生成的，ΔG 值为 10-13 kcal mol。对于所有胺的次要 N-脱烷基化产物，烷基氨基醇是一种重要的中间体，可能通过自由基反应途径生成，ΔG 值为 21-34 kcal mol。此外，本研究还比较了脂肪胺、羟胺和烷基氨基醇与臭氧的反应活性，并对其进行了阐明。预计这些结果将扩展我们对臭氧化过程中含氮化合物降解机制的理解。
