Nulakani Naga Venkateswara Rao, Ali Mohamad Akbar
Department of Chemistry, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates.
Center for the Catalyst and Separations, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates.
Front Chem. 2024 May 30;12:1407355. doi: 10.3389/fchem.2024.1407355. eCollection 2024.
Aminomethanol is released into the atmosphere through various sources, including biomass burning. In this study, we have expounded the chemical kinetics of aminomethanol in the reaction pathways initiated by the hydroxyl radical ( H) with the aid of //density functional theory (DFT) , coupled-cluster theory (CCSD(T))//hybrid-DFT (M06-2X/6-311++G (3df, 3pd). We have explored various possible directions of the H radical on aminomethanol, as well as the formation of distinct pre-reactive complexes. Our computational findings reveal that the H transfer necessitates activation energies ranging from 4.1 to 6.5 kcal/mol from the -CH group, 3.5-6.5 kcal/mol from the -NH group and 7-9.3 kcal/mol from the -OH group of three rotational conformers. The H transfer from -CH, -NH and -OH exhibits an estimated total rate constant ( ) of approximately 1.97 × 10 cm molecule s at 300 K. The branching fraction analysis indicates a pronounced dominance of C-centered NH HOH radicals with a favorability of 77%, surpassing the N-centered HCHOH (20%) and O-centered NHCH (3%) radicals. Moreover, our investigation delves into the oxidation of the prominently favored carbon-centered NH HOH radical through its interaction with atmospheric oxygen molecules. Intriguingly, our findings reveal that formamide (NHCHO) emerges as the predominant product in the NH HOH + O reaction, eclipsing alternative outcomes such as amino formic acid (NHCOOH) and formimidic acid (HN = C(H)-OH). At atmospheric conditions pertinent to the troposphere, the branching fraction value for the formation of formamide is about 99%, coupled with a rate constant of 5.5 × 10 cm molecule s. Finally, we have scrutinized the detrimental impact of formamide on the atmosphere. Interaction of formamide with atmospheric hydroxyl radicals could give rise to the production of potentially perilous compounds such as HNCO. Further, unreacted HCHOH radicals may initiate the formation of carcinogenic nitrosamines when reacting with trace N-oxides (namely, NO and NO). This, in turn, escalates the environmental risk factors.
氨基甲醇通过包括生物质燃烧在内的各种来源释放到大气中。在本研究中，我们借助密度泛函理论（DFT）、耦合簇理论（CCSD(T)）/杂化DFT（M06 - 2X/6 - 311++G(3df, 3pd)）阐述了羟基自由基（·OH）引发的反应途径中氨基甲醇的化学动力学。我们探索了·OH自由基在氨基甲醇上的各种可能反应方向，以及不同预反应复合物的形成。我们的计算结果表明，对于三种旋转构象体，从-CH基团转移H需要4.1至6.5千卡/摩尔的活化能，从-NH基团转移H需要3.5 - 6.5千卡/摩尔，从-OH基团转移H需要7 - 9.3千卡/摩尔。在300 K时，从-CH、-NH和-OH转移H的估计总速率常数（k）约为1.97×10⁻¹⁹厘米³·分子⁻¹·秒⁻¹。分支分数分析表明，以C为中心的NH₂·HOH自由基占主导地位，占比77%，超过以N为中心的·HCHOH（20%）和以O为中心的NHCH₂·（3%）自由基。此外，我们的研究通过其与大气氧分子的相互作用深入探讨了最受青睐的以碳为中心的NH₂·HOH自由基的氧化过程。有趣的是，我们的研究结果表明，在NH₂·HOH + O反应中，甲酰胺（NHCHO）是主要产物，超过了氨基甲酸（NHCOOH）和甲亚胺酸（HN = C(H)-OH）等其他产物。在对流层相关的大气条件下，甲酰胺形成的分支分数值约为99%，速率常数为5.5×10⁻¹⁹厘米³·分子⁻¹·秒⁻¹。最后，我们审视了甲酰胺对大气的有害影响。甲酰胺与大气羟基自由基的相互作用可能会产生潜在危险的化合物，如异氰酸（HNCO）。此外，未反应的·HCHOH自由基在与痕量氮氧化物（即NO和NO₂）反应时可能引发致癌亚硝胺的形成。这反过来又增加了环境风险因素。
