Environment Research Institute, Shandong University, Qingdao, 266237, China.
College of Biological and Environmental Engineering, Binzhou University, Binzhou, 256600, China.
Environ Sci Pollut Res Int. 2021 Aug;28(31):42562-42569. doi: 10.1007/s11356-021-13539-9. Epub 2021 Apr 4.
Isoprene can react with sulfoxy radicals (SO and SO) to form organosulfur compounds in aqueous phase, and the organosulfur compounds are important compositions of secondary organic aerosols (SOAs). To make sure the specific configurations of the products and the role of SO and SO in the formation of organosulfur compounds, the reaction mechanisms are studied by theoretical calculations. The lowest Gibbs free energy barrier of addition of SO onto isoprene is 24.06 kcal mol at C4 site, and its rate constant is 1.30 × 10 M s at 298 K and 1 atm. And the Gibbs free energy barriers of addition of SO onto isoprene at C1 and C4 sites are barrierless and 0.92 kcal mol; the rate constants of these two addition processes are 6.85 × 10 and 1.17 × 10 M s at 298 K and 1 atm. It elucidates that organosulfates are easier to be formed. As for the products P1 (with alcohol group) and P2 (with aldehyde group), the lowest Gibbs free energy barrier of the formation of P1 is 3.17 kcal mol, and that of the formation of P2 is 15.84 kcal mol, which means that the product with alcohol group is easier to be formed than that with aldehyde group. This work provides a reference for the formation of organosulfur compounds in aqueous phase, and it may help to understand the SOA formation.
异戊二烯可以与亚磺酸根自由基 (SO 和 SO) 反应，在水相中形成有机硫化合物，而这些有机硫化合物是二次有机气溶胶 (SOA) 的重要组成部分。为了确定产物的特定构型以及 SO 和 SO 在有机硫化合物形成过程中的作用，通过理论计算研究了反应机制。SO 加成到异戊二烯上的最低吉布斯自由能垒为 24.06 kcal/mol，在 298 K 和 1 atm 下的速率常数为 1.30×10 M s。SO 加成到异戊二烯 C1 和 C4 位上的吉布斯自由能垒是无垒的，为 0.92 kcal/mol；这两个加成过程的速率常数分别为 6.85×10 和 1.17×10 M s 在 298 K 和 1 atm 下。这表明有机硫酸盐更容易形成。对于产物 P1（含醇基团）和 P2（含醛基团），P1 形成的最低吉布斯自由能垒为 3.17 kcal/mol，P2 形成的最低吉布斯自由能垒为 15.84 kcal/mol，这意味着含醇基团的产物比含醛基团的产物更容易形成。这项工作为水相有机硫化合物的形成提供了参考，可能有助于理解 SOA 的形成。
