Karimova Natalia V, Wang Weihong, Gerber R Benny, Finlayson-Pitts Barbara J
Department of Chemistry, University of California Irvine, CA 92697, USA.
The Institute of Chemistry and Fritz Haber Research Center, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
Environ Sci Process Impacts. 2024 Dec 11;26(12):2177-2188. doi: 10.1039/d4em00461b.
Benzothiazole (BTH) and its derivatives are amongst a group of emerging contaminants that are widely distributed in the environment due to their extensive use in many different consumer products. In air, reaction with the hydroxyl radical (OH) is expected to be a major loss process for BTH in the gas phase, but the kinetics and mechanisms are unknown. Here, we report a combination of experiments and theory to determine both the rate constant and products of the reaction of OH with the smallest member of the series, benzothiazole, in the gas phase. The mechanism first involves an attack by OH on BTH to produce several OHBTH intermediates. This is followed by O reactions with OHBTH, leading to several stable products successfully predicted by theory. Relative rate studies at 1 atm in air and 298 K using benzene as a reference gave a rate constant for the BTH + OH reaction of 2.1 ± 0.1 × 10 (1) cm per molecule per s, which translates to a lifetime in air of 5.5 days at 1 × 10 OH cm. Four hydroxybenzothiazole products reflecting attack on different carbon atoms of the benzene ring were measured (-OHBTH, where = 4, 5, 6, 7), with the relative product yields well predicted by the calculated formation energies of the pre-reaction OH⋯BTH complex. Attack of OH on the -CH of the thiazole ring leads to the formation of 2-OHBTH, representing a smaller fraction of the overall reaction, and is shown to proceed through a more complex mechanism than attack on the benzene ring. A theoretical approach to predicting chromatographic retention times of the products based on solvation free energies (Δ) was successful for most of the products. These studies illustrate how the powerful combination of experiment and theory can be used to predict products of atmospheric oxidation of emerging contaminants and ultimately used to assess their impacts on the environment.
苯并噻唑（BTH）及其衍生物是一类新兴污染物，由于它们在许多不同消费品中的广泛使用而在环境中广泛分布。在空气中，与羟基自由基（OH）的反应预计是气相中BTH的主要损失过程，但动力学和机制尚不清楚。在此，我们报告了实验和理论相结合的方法，以确定气相中OH与该系列最小成员苯并噻唑反应的速率常数和产物。该机制首先涉及OH对BTH的攻击，产生几种OHBTH中间体。随后是OH与OHBTH的反应，产生几种理论成功预测的稳定产物。在1个大气压的空气和298 K下使用苯作为参考进行的相对速率研究得出，BTH + OH反应的速率常数为2.1±0.1×10⁻¹¹ cm³每分子每秒，这意味着在1×10⁻⁵ OH cm⁻³的情况下，在空气中的寿命为5.5天。测量了反映对苯环不同碳原子攻击的四种羟基苯并噻唑产物（-OHBTH，其中 = 4、5、6、7），预反应OH⋯BTH络合物的计算形成能很好地预测了相对产物产率。OH对噻唑环-CH的攻击导致2-OHBTH的形成，占总反应的比例较小，并且显示出比攻击苯环更复杂的机制。基于溶剂化自由能（Δ）预测产物色谱保留时间的理论方法对大多数产物是成功的。这些研究说明了实验和理论的强大结合如何可用于预测新兴污染物大气氧化的产物，并最终用于评估它们对环境的影响。
