Horváth Attila K, Nagypál István, Epstein Irving R
Department of Physical Chemistry, University of Szeged, P.O.Box 105, Szeged H-6701, Hungary.
Inorg Chem. 2006 Nov 27;45(24):9877-83. doi: 10.1021/ic061332t.
The chlorite-tetrathionate reaction has been studied spectrophotometrically in the pH range of 4.65-5.35 at T = 25.0 +/- 0.2 degrees C with an ionic strength of 0.5 M, adjusted with sodium acetate as a buffer component. The reaction is unique in that it demonstrates autocatalysis with respect to the hydrogen and chloride ion products and the key intermediate, HOCl. The thermodynamically most-favorable stoichiometry, 2S(4)O(6)2- + 7ClO2- + 6H2O --> 8SO(4)2- + 7Cl- + 12H+, is not found. Under our experimental conditions, chlorine dioxide, the chlorate ion, or both are detected in appreciable amounts among the products. Initial rate studies reveal that the formation of chlorine dioxide varies in an unusual way, with the chlorite ion acting as a self-inhibitor. The reaction is supercatalytic (i.e., second order with respect to autocatalyst H+). The autocatalytic behavior with respect to Cl- comes from chloride catalysis of the chlorite-hypochlorous acid and hypochlorous acid-tetrathionate subsystems. A detailed kinetic study and a model that explains this unusual kinetic behavior are presented.
在25.0±0.2℃、离子强度为0.5M（用醋酸钠作为缓冲成分进行调节）的条件下，采用分光光度法研究了亚氯酸盐 - 连四硫酸盐反应，pH范围为4.65 - 5.35。该反应的独特之处在于，它对氢离子、氯离子产物以及关键中间体次氯酸表现出自催化作用。未发现热力学上最有利的化学计量关系：2S(4)O(6)2- + 7ClO2- + 6H2O --> 8SO(4)2- + 7Cl- + 12H+。在我们的实验条件下，产物中会检测到相当数量的二氧化氯、氯酸根离子或两者都有。初始速率研究表明，二氧化氯的形成方式不同寻常，亚氯酸根离子起到了自抑制剂的作用。该反应是超催化的（即对自催化剂H+为二级反应）。对Cl-的自催化行为源于亚氯酸盐 - 次氯酸和次氯酸 - 连四硫酸盐子系统的氯化物催化作用。本文给出了详细的动力学研究以及解释这种异常动力学行为的模型。
