ELKH-DE Mechanisms of Complex Homogeneous and Heterogeneous Chemical Reactions Research Group, University of Debrecen, Egyetem tér 1, Debrecen 4032, Hungary.
Doctoral School of Chemistry, University of Debrecen, Egyetem tér 1, Debrecen H-4032, Hungary.
Inorg Chem. 2023 Apr 10;62(14):5426-5434. doi: 10.1021/acs.inorgchem.2c04329. Epub 2023 Mar 28.
An advanced experimental protocol is reported for studying the kinetics and mechanism of the complex redox reaction between chlorite ion and hypochlorous acid under acidic condition. The formation of ClO is followed directly by the classical two-component stopped-flow method. In sequential stopped-flow experiments, the target reaction is chemically quenched using NaI solution and the concentration of each reactant and product is monitored as a function of time by utilizing the principles of kinetic discrimination. Thus, in contrast to earlier studies, not only the formation of one of the products but the decay of the reactants was also directly followed. This approach provides a firm basis for postulating a detailed mechanism for the interpretation of the experimental results under a variety of conditions. The intimate details of the reaction are explored by simultaneously fitting 78 kinetic traces, i.e., the concentration vs. time profiles of ClO, HOCl, and ClO, to an 11-step kinetic model. The most important reaction steps were identified, and it was shown that two reactive intermediates have a pivotal role in the mechanism. While chlorate ion predominantly forms via the reaction of ClO, chlorine dioxide is exclusively produced in reaction steps involving ClO. This study leads to clear conclusions on how to control the stoichiometry of the reaction and achieve optimum conditions to produce chlorine dioxide and to reduce the formation of the toxic chlorate ion in practical applications.
本文报道了一种先进的实验方案，用于研究酸性条件下亚氯酸根离子与次氯酸之间复杂氧化还原反应的动力学和反应机制。ClO 的形成直接采用经典的双组分停流法进行跟踪。在连续停流实验中，目标反应通过 NaI 溶液进行化学猝灭，通过动力学判别原理，随时间监测各反应物和产物的浓度。因此，与早期研究相比，不仅直接跟踪了其中一个产物的形成，还直接跟踪了反应物的衰减。该方法为根据各种条件下的实验结果提出详细的反应机制提供了坚实的基础。通过同时拟合 78 个动力学轨迹，即 ClO、HOCl 和 ClO 的浓度随时间的变化曲线，对 11 步动力学模型进行分析，探索了反应的细节。确定了最重要的反应步骤，并表明两个反应中间体在反应机制中起着关键作用。虽然氯酸根离子主要通过 ClO 的反应形成，但二氧化氯仅在涉及 ClO 的反应步骤中产生。本研究得出了明确的结论，即在实际应用中如何控制反应的化学计量比，以达到产生二氧化氯的最佳条件，并减少有毒氯酸根离子的形成。
