Key Laboratory of Cluster Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China.
School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China.
Chemosphere. 2018 Dec;212:504-512. doi: 10.1016/j.chemosphere.2018.08.074. Epub 2018 Aug 22.
New particle formation (NPF) process has been observed frequently in various environments and produces a large fraction of atmospheric aerosols. However, the chemical species participating in the nucleation as well as the corresponding nucleation mechanism in the atmosphere still remain ambiguous. Recent research by Leopold et al. shows that cycloaddition reaction of SO to carboxylic acids could contribute to the formation of organic sulfuric anhydride which would have lower vapor pressure compared with the corresponding carboxylic acid and hence kick-start new particle formation in the gas phase. In the present study, energy profile for the formation of 3-methyl-1,2,3-butanetricarboxylic sulfuric anhydride (MBTCSA) through the cycloaddition of SO to 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) has been investigated using computational methods. As a result, such a process would be effectively barrierless for one of the terminal carboxy group and has very low energy barriers for the other two carboxy groups (0.6 and 2.8 kcal/mol, respectively), indicating the whole process is a plausible gas phase pathway to MBTCSA formation. Furthermore, by evaluating the stability of the generated atmospheric clusters through topological and kinetic analysis, interaction between atmospheric nucleation precursor with MBTCSA is found to be more thermodynamically favourable and stronger than those with sulfuric acid and MBTCA which is identified from further-generation oxidation of a-pinene. Hence MBTCSA is speculated to be a potential participator in the initial new particle formation and the further particles growth.
新粒子形成（NPF）过程在各种环境中经常被观察到，并产生了大气气溶胶的很大一部分。然而，参与成核的化学物质以及大气中的相应成核机制仍然不清楚。Leopold 等人最近的研究表明，SO 与羧酸的环加成反应可能有助于形成有机硫酸酐，与相应的羧酸相比，其蒸气压较低，因此会在气相中引发新粒子的形成。在本研究中，使用计算方法研究了 SO 与 3-甲基-1,2,3-丁烷三羧酸（MBTCA）通过环加成反应形成 3-甲基-1,2,3-丁烷三羧酸硫酸酐（MBTCSA）的形成能谱。结果表明，对于其中一个末端羧基，该过程将有效地无势垒，而对于另外两个羧基，其能量势垒非常低（分别为 0.6 和 2.8 kcal/mol），表明整个过程是 MBTCSA 形成的一种合理的气相途径。此外，通过拓扑和动力学分析评估生成的大气团簇的稳定性，发现与大气成核前体的相互作用与硫酸和 MBTCA 相比更有利于热力学和更强，这是从α-蒎烯的进一步氧化中确定的。因此，MBTCSA 被推测为初始新粒子形成和进一步粒子生长的潜在参与者。
