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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Autocatalysis-Driven Clock Reaction III: Clarifying the Kinetics and Mechanism of the Thiourea Dioxide-Iodate Reaction in an Acidic Medium
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Autocatalysis-Driven Clock Reaction III: Clarifying the Kinetics and Mechanism of the Thiourea Dioxide-Iodate Reaction in an Acidic Medium

机译：自催化驱动的时钟反应III：澄清硫醚 - 碘酸碘酸盐反应在酸性介质中的动力学和机制

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摘要

The thiourea dioxide-iodate reaction has been reinvestigated spectrophotometrically under acidic conditions using phosphoric acid-dihydrogen phosphate buffer within the pH range of 1.1-1.8 at 1.0 M ionic strength adjusted by sodium perchlorate and at 25 degrees C. The system was found to exhibit clock behavior, having a well-defined and reproducible time lag called Landolt time, though elementary iodine may even be detected in substrate excess; hence, under these conditions, the reaction can be classified as an autocatalysis-driven clock reaction. It is clearly demonstrated that the previously proposed kinetic model suffers from serious drawbacks from both theoretical and experimental points of view. The reaction may be characterized by either sigmoidal-shaped or rise-and-fall kinetic traces, depending on the initial concentration ratio of the reactants. Iodide significantly accelerates the appearance of the clock species iodine acting therefore as an autocatalyst. The age of stock TDO solution also has a great, so far completely overlooked impact on the Landolt time. On the basis of evaluating simultaneously the kinetic curves, a 16 step kinetic model including 5 well-known rapidly established equilibria is proposed with 7 fitted rate coefficients in which the rate coefficients of both forms of TDO were determined.
机译：使用磷酸二氢磷酸盐缓冲液在1.1-1.8的pH范围内的酸性条件下，在1.0M离子强度下通过高氯酸钠和25℃调节的离子强度，发现二氧化磷酸二氧化碘化物反应。发现该系统表现出时钟行为，具有良好的定义和可重复的时间滞后称为抵抗时间，但甚至可以在衬底上检测到基本碘;因此，在这些条件下，反应可以被分类为自催化驱动的时钟反应。清楚地证明，先前提出的动力学模型来自理论和实验观点的严重缺点。反应可根据六样形或上升动力学迹线的特征在于，取决于反应物的初始浓度比。碘化物显着加速了时钟物种碘作用的外观作为自催化剂。股票时代TDO解决方案也有一个伟大的，到目前为止对抵抗时间完全忽略了影响。在同时评估动力学曲线的基础上，提出了一种包括5众所周知的快速建立的平衡的16步动态模型，其中具有7个拟合速率系数，其中确定了两种形式的TDO的速率系数。

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